Charmless Hadronic Two-body Decays of the B_s Mesons

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Open Charm and Beauty Production at HERA

a r X i v :h e p -e x /0011034v 1 10 N o v 2000OPEN CHARM AND BEAUTY PRODUCTION AT HERAFELIX SEFKOW(on behalf of the H1and ZEUS Collaborations)Physik-Institut der Universit¨a t Z¨u rich,Winterthurerstr.190,CH-8057Z¨u rich,SwitzerlandE-mail:felix.sefkow@desy.deSelected new results from the H1and ZEUS collaborations on ep interactions at 300-318GeV centre-of-mass energy are presented.The full pre-upgrade integrated luminosity of HERA of 110pb −1is used.Charm cross sections are measured up to high values of x B and Q 2and are found to be well described by NLO QCD in the 3ﬂavour scheme.Orbitally excited D mesons are observed;radial excitations are searched for,but are not seen.The ﬁrst b cross section measurement is conﬁrmed with a lifetime based method,establishing the excess over NLO QCD.1CharmThanks to the excellent HERA performance the available statistics has strongly increased.ZEUS now has a signal of 27,000D ∗de-cays in the “golden”mode D ∗→D 0π+→K −π+π+.This wealth of data (similarly at hand for H1)allows perturbative QCD to be tested with charm production data in an ex-tended kinematic range and opens the possi-bility for charm spectroscopy at HERA.In QCD,heavy quark production in ep interactions predominantly proceeds via bo-son gluon fusion (BGF),where a quark anti-quark pair is created in the interaction of a photon with a gluon in the proton (3Flavour scheme).At four-momentum transfers much higher than the charm quark mass,Q 2≫m 2c ,such a description becomes inaccurate,and a treatment in terms of charm densities in the proton may be more adequate.The single-diﬀerential D ∗cross sections measured in deep inelastic scattering (DIS)by ZEUS 1as a function of Bjorken-x and Q 2now cover a range up to x B ≃0.1and Q 2≃1000GeV 2.(Fig.1)They are com-pared with NLO calculations in the 3Flavour scheme 2,which use as input gluon densities from global ﬁts 3or a parameter-ization extracted from scaling violations of the proton structure function F 2,measured at HERA.Good agreement is seen,showing that the BGF picture provides an overall con-101010110log 10(Q 2) (GeV 2)d σ / l o g 10(Q 2) (n b / Ge V 2)Figure 1.D ∗cross section in DIS vs.NLO QCD in the 3Flavour scheme (shaded:m c =1.3−1.6GeV).sistent description of charm production and inclusive DIS up to high x B and Q 2.The spectrum of non-strange D mesons is only partially established experimentally.Apart from the lowest mass D and D ∗states,the narrow excited P-wave mesons D 1(2420)and D ∗2(2460)have been ﬁrmly identiﬁed,with spin-parity J P =1+and 2+.A nar-row state interpreted as radially excited D ∗′±has been observed by DELPHI 4,but was not conﬁrmed by OPAL and CLEO searches 5.ZEUS report 6the observation of or-bitally excited D 01and D ∗02mesons in the de-cay channel D (∗)0J →D ∗+π−+c.c.From a ﬁt to the invariant mass (Fig.2)and π−he-licity angle distributions they extract relative production rates ofD 01→D ∗+π−M(K ππs π4) - M(K ππs ) + M(D *) (GeV)C o m b i n a t i o n s / 5 M e V150175200225250275300325350C o m b i n a t i o n s / 5 M e VM(K ππs π4) - M(K ππs ) + M(D *) (GeV)Figure 2.Mass diﬀerence distribution for D ∗∗0can-didates.The curves show ﬁts using mass and helicity angle information.D ∗02→D∗+π−D ∗+<2.3%(at 95%C.L.)which indicates that the search has a sen-sitivity corresponding to about the size of the claimed DELPHI signal.Since at HERA almost all charmed mesons originate from prompt charm production,and feed-down from beauty can be neglected,a rather tight limit on D ∗′±production in charm fragmen-tation can be set (at 95%C.L.):f (c →D ∗′+)·BR(D ∗′+→D ∗+π+π−)<0.7%50100150M(K ππs π4π5) - M(K ππs ) + M(D *) (GeV)Figure 3.Mass diﬀerence distribution for D ∗′±can-didates.The search region contains 91±75candi-dates over the ﬁtted background.The insert shows a Monte Carlo signal normalized to the quoted limit.2BeautyBeauty production at HERA is suppressed with respect to charm by two orders of mag-nitude.The measurements so far rely on in-clusive semi-leptonic decays,using as signa-ture the high mass of the b quark by observ-ing the transverse momentum p rel T of the lep-ton relative to a jet,and also its long lifetime by observing tracks from secondary vertices.The ﬁrst measurement by H17,using the p rel T method,revealed a b photoproduction cross section almost a factor of 2above theoretical prediction 8(Fig.4).The new H1measurement 9also usesphotoproduction dijet events,where now at least one muon is measured in the two-layer silicon vertex detector.The signed impact parameter δis determined in the plane trans-verse to the beam,axis,and the distribution is decomposed by a maximum likelihood ﬁt which adjusts the relative contributions frombeauty,charm and fake muons to the sample(Fig.5).The ﬁt describes the data well and translates into a b cross section that,usingW γp [GeV ]σ(γp →b b −X ) [n b ]Figure 4.b photoproduction cross section vs.NLO QCD,using diﬀerent proton structure functions (shaded:scale uncertainty).an independent signature and new data,con-ﬁrms the published result,based on 1996data and a diﬀerent set of cuts.The δspectrum for a sample with higherb purity,obtained by a cut p rel T >2GeV (Fig.6)agrees well with the prediction from the δﬁt to the full sample.Since the two observables are consistent,they can be combined in a likelihood ﬁt of the two-dimensional (δ,p rel T )distribution.The result,averaged with the published number,is σ(ep →b ¯bX →µX )=(170±25)pb in the range Q 2<1GeV 2,0.1<y <0.8,p T (µ)>2GeV,35◦<θ(µ)<130◦.This is higher than the NLO QCD prediction of (104±17)pb based on 8.Such a discrepancy between experiment and NLO QCD is now established in both ep and ¯p p interactions.References1.ZEUS Coll.,D ∗±Production in Deep In-elastic Scattering ,contrib.paper no.449.2.B.W.Harris and J.Smith,Phys.Rev.D 57,2806(1998).3.M.Glueck,E.Reya and A Vogt,hep-ph/9806404;i et al.,hep-ph/9903282.4.DELPHI Coll.,Phys.Lett.B 426,231(1998).11010M u o n s / 50 µmFigure for muons.(The sign depends on whether the track in-tersects the jet axis upstream or downstream (+)of the primary event vertex.)0204060δ [ cm ]M u o n s / 50 µmFigure 6.Impact parameter distribution for muons with p rel T >2GeV.with the absolute prediction from the ﬁt to the full sample.5.OPAL Coll.,contrib.paper to ICHEP 98,OPAL PN 352;CLEO Coll.,hep-ex/9901008.6.ZEUS Coll.,Production of P-Wave Charm Mesons at HERA ,contrib.paper no.448.7.H1Coll.,Phys.Lett.B 467,156(1999).8.S.Frixione,M.L.Mangano,P.Nason and G.Ridolﬁ,Phys.Lett.B 348,633(1995).9.H1Coll.,Measurement of the Beauty Production Cross Section at HERA Us-ing Lifetime Information ,contrib.paper no.311.。

Inclusive weak decay rates of heavy hadrons

a r X i v :h e p -p h /0004257v 1 27 A p r 2000Theoretical Physics InstituteUniversity of MinnesotaTPI-MINN-00/17UMN-TH-1851-00April 2000Inclusive weak decay rates of heavy hadrons M.B.Voloshin Theoretical Physics Institute,University of Minnesota,Minneapolis,MN 55455and Institute of Theoretical and Experimental Physics,Moscow,117259Expanded version of a contribution to the ﬁnal report book of the Fermilab Workshop on B Physics at Tevatron Abstract A compact review of the theory,including some recent developments,of inclusive weak decay rates of charmed and b hadrons with an emphasis on predictions that can be tested in the forthcoming experiments.1IntroductionThe dominant weak decays of hadrons containing a heavy quark,c or b,are caused by the decay of the heavy quark.In the limit of a very large mass m Q of a heavy quark Q the parton picture of the hadron decay should set in,where the inclusive decay rates of hadrons, containing Q,mesons(Q¯q)and baryons(Qqq),are all the same and equal to the inclusive decay rateΓparton(Q)of the heavy quark.Yet,the known inclusive decay rates[1]are conspicuously diﬀerent for diﬀerent hadrons,especially for charmed hadrons,whose lifetimes span a range of more than one order of magnitude from the shortestτ(Ωc)=0.064±0.020 ps to the longestτ(D+)=1.057±0.015ps,while the diﬀerences of lifetime among b hadrons are substantially smaller.The relation between the relative lifetime diﬀerences for charmed and b hadrons reﬂects the fact that the dependence of the inclusive decay rates on the light quark-gluon‘environment’in a particular hadron is a pre-asymptotic eﬀect in the parameter m Q,which eﬀect vanishes as an inverse power of m Q at large mass.A theoretical framework for systematic description of the leading at m Q→∞term in the inclusive decay rateΓparton(Q)∝m5Q as well as of the terms relatively suppressed by inverse powers of m Q is provided[2,3,4]by the operator product expansion(OPE)in m−1Q. Existing theoretical predictions for inclusive weak decay rates are in a reasonable agreement, within the expected range of uncertainty,with the data on lifetimes of charmed particles and with the so far available data on decays ofB mesons.The only outstanding piece of present experimental data is on the lifetime of theΛb baryon:τ(Λb)/τ(B d)≈0.8,for which ratio a theoretical prediction,given all the uncertainty involved,is unlikely to produce a number lower than0.9.The number of available predictions for inclusive decay rates of charmed and b hadrons is suﬃciently large for future experimental studies toﬁrmly establish the validity status of the OPE based theory of heavy hadron decays,and,in particular,toﬁnd out whether the present contradiction between the theory and the data onτ(Λb)/τ(B d)is a temporary diﬃculty,or an evidence of fundamentalﬂaws in theoretical understanding.It is a matter of common knowledge that application of OPE to decays of charmed and b hadrons has potentially two caveats.One is that the OPE is used in the Minkowsky kinematical domain,and therefore relies on the assumption of quark-hadron duality at the energies involved in the corresponding decays.In other words,it is assumed that suﬃciently many exclusive hadronic channels contribute to the inclusive rate,so that the accidentals of the low-energy resonance structure do not aﬀect the total rates of the inclusive processes. Theoretical attempts at understanding the onset of the quark-hadron duality are so farlimited to model estimates[5,6],not yet suitable for direct quantitative evaluation of possible deviation from duality in charm and b decays.This point presents the most fundamental uncertainty of the OPE based approach,and presently can only be clariﬁed by confronting theoretical predictions with experimental data.The second possible caveat in applying the OPE technique to inclusive charm decays is that the mass of the charm quark,m c,may be insuﬃciently large for signiﬁcant suppression of higher terms of the expansion in m−1c. The relative lightness of the charm quark,however,accounts for a qualitative,and even semi-quantitative,agreement of the OPE based predictions with the observed large spread of the lifetimes of charmed hadrons:the nonperturbative eﬀects,formally suppressed by m−2c and m−3c are comparable with the‘leading’parton term and describe the hierarchy of the lifetimes.Another uncertainty of a technical nature arises from poor knowledge of matrix elements of certain quark operators over hadron,arising as terms in OPE.These can be estimated within theoretical models,with inevitable ensuing model dependence,or,where possible, extracted from the experimental data.With these reservations spelled out,we discuss here the OPE based description of inclusive weak decays of charm and b hadrons,with emphasis on speciﬁc experimentally testable predictions,and on the measurements,which would less rely on model dependence of the estimates of the matrix elements,thus allowing to probe the OPE predictions at a fundamental level.2OPE for inclusive weak decay ratesThe optical theorem of the scattering theory relates the total decay rateΓH of a hadron H Q containing a heavy quark Q to the imaginary part of the‘forward scattering amplitude’.For the case of weak decays the latter amplitude is described by the following eﬀective operatorL eff=2Im i d4x e iqx T{L W(x),L W(0)} ,(1) in terms of which the total decay rate is given by1ΓH= H Q|L eff|H Q .(2) The correlator in equation(1)in general is a non-local operator.However at q2=m2Q the dominating space-time intervals in the integral are of order m−1Q and one can expand thecorrelator in x ,thus producing an expansion in inverse powers of m Q .The leading term in this expansion describes the parton decay rate of the quark.For instance,the term in the non-leptonic weak Lagrangian √q 1L γµQ L )(64π3ηnlq 3,due to the relation H Q |64π3 64π3 4π i c (3)i (Q Γ′i Q ),(4)where the superscripts denote the power of m −1Q in the relative suppression of the correspond-ing term in the expansion with respect to the leading one,G µνis the gluon ﬁeld tensor,q i stand for light quarks,u,d,s ,and,ﬁnally,Γi ,Γ′i denote spin and color structures of the four-quark operators.The coeﬃcients c (a )depend on the speciﬁc part of the weak interaction Lagrangian L W ,describing the relevant underlying quark process.One can notice the absence in the expansion (4)of a term suppressed by just one power of m −1Q ,due to non-existence of operators of suitable dimension.Thus the decay rates receiveno correction of relative order m −1Q in the limit of large m Q ,and the ﬁrst pre-asymptoticcorrections appear only in the order m −2Q .The mechanisms giving rise to the three discussed terms in OPE are shown in Figure 1.The ﬁrst,leading term corresponds to the parton decay,and does not depend on the light guark and gluon ‘environment’of the heavy quark in a hadron.The second term describes the eﬀect on the decay rate of the gluon ﬁeld that a heavy quark ‘sees’in a hadron.This term in fact is sensitive only to the chromomagnetic part of the gluon ﬁeld,and contains the operator of the interaction of heavy quark chromomagnetic moment with the chromomagnetic ﬁeld.Thus this term depends on the spin of the heavy quark,but does not depend on theﬂavors of the light quarks or antiquarks.Therefore this eﬀect does not split the inclusive decay rates withinﬂavor SU(3)multiplets of heavy hadrons,but generally gives diﬀerence of the rates, say,between mesons and baryons.The dependence on the light quarkﬂavor arises from the third term in the expansion(4)which explicitly contains light quarkﬁelds.Historically, this part is interpreted in terms of two mechanisms[2,8,9]:the weak scattering(WS)and the Pauli interference(PI).The WS corresponds to a cross-channel of the underlying decay, generically Q→q1q2q1,weak-scatters(annihilates)in the process q3.The Pauli interference eﬀect arises when one of theﬁnal(anti)quarks in the decay of Q is identical to the spectator(anti)quark in the hadron,so that an interference of identical particles should be taken into account.The latter interference can be either constructive or destructive,depending on the relative spin-color arrangement of the(anti)quark produced in the decay and of the spectator one,thus the sign of the PI eﬀect is found only as a result of speciﬁc dynamical calculation.In speciﬁc calculations,however,WS and PI arise from the same terms in OPE,depending on the hadron discussed,and technically there is no need to resort to the traditional terminology of WS and PI.q3q3--Q QQ QP P PPq qm5Q(Q( σ· B)Q m2Q(QΓ′Q)vvvFigure1:Graphs for threeﬁrst terms in OPE for inclusive decay rates:the parton term, the chromomagnetic interaction,and the four-quark term.In what follows we discuss separately the eﬀects of the three terms in the expansion(4) and their interpretation within the existing and future data.3The parton decay rateThe leading term in the OPE amounts to the perturbative expression for the decay rate of a heavy quark.In b hadrons the contribution of the subsequent terms in OPE is at the level of few percent,so that the perturbative part can be confronted with the data in its own right. In particular,for the B d meson the higher terms in OPE contribute only about1%of the total non-leptonic as well as of the semileptonic decay rate.Thus the data on these rates can be directly compared with the leading perturbative term in OPE.The principal theoretical topic,associated with this term is the calculation of QCD radiative corrections,i.e.of the factorηnl in eq.(3)and of a similar factor,ηnl,for semileptonic decays.It should be noted,that even at this,perturbative,level there is a known long-standing problem between the existing data and the theory in that the current world average for the semileptonic branching ratio for the B mesons,B sl(B)=10.45±0.21%,is somewhat lower than the value B sl(B)≥11.5preferred from the present knowledge of theoretical QCD radiative corrections to the ratio of non-leptonic to semileptonic decay rates(see e.g.[10]). However,this apparent discrepancy may in fact be due to insuﬃcient‘depth’of perturbative QCD calculation of the ratioηnl/ηsl.In order to brieﬂy elaborate on this point,we notice that the standard way of analyzing the perturbative radiative corrections in the nonleptonic decays is through the renormalization group(RG)summation of the leading log terms and the ﬁrst next-to-leading terms[11,12]in the parameter L≡ln(m W/m b).For the semileptonic decays the logarithmic dependence on m W/m b is absent in all orders due to the weak current conservation at momenta larger than m b,thus the correction is calculated by the standard perturbative technique,and a complete expression in theﬁrst order inαs is available both for the total rate[13,14]and for the lepton spectrum[15].In reality however the parameter L≈2.8is not large,and non-logarithmic terms may well compete with the logarithmic ones. This behavior is already seen from the known expression for the logarithmic terms:when expanded up to the orderα2s the result of Ref.[16]for the rate of decays with singleﬁnal charmed quark takes the formΓ(b→c¯u d)+Γ(b→c¯u s)π+α2s6+2c(a)is known explicitly[16]and is quite weak:c(0)=19/2,c(1)=6,and c(m2c/m2b)≈9.0for the realistic mass ratio m c/m b≈0.3.One can see that the term with the single logarithm L contributes about two thirds of that with L2in the term quadratic inαs.Under such circumstances the RG summation of the terms with powers of L does not look satisfactory for numerical estimates of the QCD eﬀects,at least at the so far considered level of theﬁrst next-to-leading order terms,and the next-to-next-to-leading terms can be equally important as the two known ones,which would eliminate the existing impasse between the theory and the data on B sl(B).One can present some arguments[17]that this is indeed the case for the b quark decay,although a complete calculation of these corrections is still unavailable.4Chromomagnetic and time dilation eﬀects in decay ratesThe corrections suppressed by two powers of m−1Q to inclusive decay rates arise from two sources[7]:the O(m−2Q)corrections to the matrix element of the leading operator,(QQ|H Q =1−µ2π(H Q)−µ2g(H Q)Q(i D)2Q|H Q ,µ2g= H Q|2σµνGµνQ|H Q ,(7) with D being the QCD covariant derivative.The correction in equation(6)in fact corre-sponds to the time dilation factor m Q/E Q,for the heavy quark decaying inside a hadron, where it has energy E Q,which energy is contributed by the kinetic part(∝µ2π)and the chromomagnetic part(∝µ2g).The second term in OPE describes the eﬀect of the chromo-magnetic interaction in the decay process,and is also expressed throughµ2g.The explicit formulas for the decay rates,including the eﬀects up to the order m−2Q are found in[7]and for decays of the b hadrons read as follows.For the semileptonic decay rate Γsl(H b)=|V cb|2G2F m5b bb|H b 1+µ2g2dand for the non-leptonic decay rateΓnl(H b)=|V cb|2G2F m5b bb|H b 1+µ2g2d m2b I2(x) .(9) These formulas take into account only the dominant CKM mixing V cb and neglect the small one,V ub.The following notation is also used:x=m c/m b,I0(x,y,z)stands for the kinemat-ical suppression factor in a three-body weak decay due to masses of theﬁnal fermions.In particular,I0(x,0,0)=(1−x4)(1−8x2+x4)−24x4ln x,(10)I0(x,x,0)=(1−14x2−2x4−12x6)√1−4x21−4x2. Furthermore,I(x)=I0(x,0,0)+I0(x,x,0),andI2(x)=(1−x2)3+ 1+11−4x2−3x2(1−2x4)ln1+√1−√αs(m W) 4/b,(11)and b is the coeﬃcient in the QCD beta function.The value of b relevant to b decays is b=23/3.Numerically,for x≈0.3,the expressions for the decay rates can be written asΓsl(H b)=Γpartonsl 1−µ2π(H b)−µ2g(H b)m2b ,Γnl(H b)=Γpartonnl 1−µ2π(H b)−µ2g(H b)m2b ,(12)whereΓparton is the perturbation theory value of the corresponding decay rate of b quark.The matrix elementsµ2πandµ2g are related to the spectroscopic formula for a heavy hadron mass M,M(H Q)=m Q+2m Q + (13)Being combined with the spin counting for pseudoscalar and vector mesons,this formula allows toﬁnd the value ofµ2g in pseudoscalar mesons from the mass splitting:µ2g(B)=3Γnl(B)=1−µ2π(Λb)−µ2π(B)m2b.(15)The diﬀerence of the kinetic terms,µ2π(Λb)−µ2π(B),can be estimated from the mass formula:µ2π(Λb)−µ2π(B)=2m b m cM(B)−M is the spin-averaged mass of the mesons,e.g.with respect to those of the charmed hyperons in a reasonable agreement with the observed pattern of the lifetimes.It should be emphasized once again that the m−2Q eﬀects do not depend on theﬂavors of the spectator quarks or antiquarks.Thus the explanation of the variety of the inclusive decay rates within theﬂavor SU(3)multiplets,observed for charmed hadrons and expected for the b ones,has to be sought among the m−3Q terms.5L(3)eff.Coeﬃcients and operatorsAlthough the third term in the expansion(4)is formally suppressed by an extra power of m−1Q,its eﬀects are comparable to,or even larger than the eﬀects of the second term.This is due to the fact that the diagrams determining the third term(see Fig.1)contain a two-body phase space,while theﬁrst two terms involve a three-body phase space.This brings in a numerical enhancement factor,typically4π2.The enhanced numerical signiﬁcance of the third term in OPE,generally,does not signal a poor convergence of the expansion in inverse heavy quark mass for decays of b,and even charmed,hadrons the numerical enhancement factor is a one time occurrence in the series,and there is no reason for similar‘anomalous’enhancement among the higher terms in the expansion.Here weﬁrst present the expressions for the relevant parts of L(3)eff for decays of b and c hadrons in the form of four-quark operators and then proceed to a discussion of hadronic matrix elements and the eﬀects in speciﬁc inclusive decay rates.The consideration of the eﬀects in decays of charmed hadrons is interesting in its own right,and leads to new predic-tions to be tested experimentally,and is also important for understanding the magnitude of the involved matrix elements using the existing data on charm decays.,induced We start with considering the term L(3)eff in b hadron non-leptonic decays,L(3,b)eff,nlby the underlying processes b→c c s,b→c c d.Unlike the case of three-body decay,the kinematical diﬀerence between the two-body states c u,involvedis of the order of m2c/m2b≈0.1and is rather small.At present level in calculation of L(3,b)eff,nlof accuracy in discussing this term in OPE,one can safely neglect the eﬀect ofﬁnite charmedreads as[4]quark mass2.In this approximation the expression for L(3,b)eff,nl=|V bc|2G2F m2b bΓµb)(bΓµu)(L(3,b)eff,nl2The full expression for aﬁnite charmed quark mass can be found in[21]˜C5(3q Γµq )+˜C 6(3q k Γµq i )+(17)1b Γµt a b )j a µ−(5˜C 2++˜C 2−−6˜C +˜C −)(3q Γq )=(s Γs )is used,the indices i,k are the color triplet ones,Γµ=γµ(1−γ5),and j a µ=dγµt a d +3(1−κ1/2)(˜C 2+−˜C 2−),˜C2=κ1/2(˜C 2+−˜C 2−),˜C 3=−13(1−κ1/2)(5˜C2++˜C 2−+6˜C +˜C −) ,˜C4=−14(˜C ++˜C −)2+14κ1/2(5˜C 2++˜C 2−−6˜C +˜C −).(18)The expression for the CKM dominant semileptonic decays of b hadrons,associated with the elementary process b →c ℓνdoes not look to be of an immediate interest.The reason is that this process is intrinsically symmetric under the ﬂavor SU(3),and one expects no signiﬁcant splitting of the semileptonic decay rates within SU(3)multiplets of the b hadrons.The only possible eﬀect of this term,arising through a penguin-like mechanism can be in a small overall shift of semileptonic decay rates between B mesons and baryons.However,these eﬀects are quite suppressed and are believed to be even smaller than the ones arisingform the discussed m −2b terms.For charm decays there is a larger,than for b hadrons,variety of eﬀects associated with L (3)eff ,that can be studied experimentally,and we present here the relevant parts of the eﬀective Lagrangian.For the CKM dominant non-leptonic decays of charm,originatingfrom the quark process c →s u4πC 1(d Γµd )+C 2(d Γµc )+C 3(3s Γµs )+C 4(3s k Γµs i )+(19)C 5(3u Γµu )+C 6(3u k Γµu i )+1c Γµt a c )j a µ−(5C 2++C 2−)(3s and c →d u4π{C 1(q Γµq )+C 2(q k Γµq i )+C 3(3q Γµq )+C 4(3q k Γµq i )+(20)2C 5(3u Γµu )+2C 6(3u k Γµu i )+2c Γµt a c )j a µ−(5C 2++C 2−)(3q Γq )=(s Γs )is used.The semileptonic decays of charm,the CKM dominant,associated with c →s ℓν,and the CKM suppressed,originating from c →s ℓν,contribute to the semileptonic decay rate,which certainly can be measured experimentally.The expression for the part of the eﬀectiveLagrangian,describing the m −3Q terms in these decays is [17,24,25]L (3)eff,sl =G 2F m 2cc Γµc +2cγµγ5c )(c i Γµc k +2c i γµγ5c k )(3Even if the inclusive rate of these decays is not to be separated experimentally,they contribute about 10%of the total decay rate,and it is worthwhile to include their contribution in the balance of the total width.sin2θc L1(3dΓµd)+L2(3d kΓµd i) −2κ1/2(κ−2/9−1)(3B s oscillations. The data on decay rates of the cascade hyperonΞ0b are not yet available,while the currently measured lifetimes of B d and B s are within less than2%from one another.Theoretically, the diﬀerence of the lifetimes,associated with possible violation of the SU(3)symmetry and with breaking of the U symmetry of the eﬀective Lagrangian(17),is expected to not exceed about1%.For the non-vanishing matrix elements of four-quark operators over pseudoscalar mesons one traditionally starts with the factorization formula and parametrizes possible deviation from factorization in terms of‘bag constants’.Within the normalization convention adopted here the relations used in this parametrization read asP Q QΓµq)(q =1P QQ ΓµQ )(q =1q stands for pseudoscalar meson made of Q and8π (˜C 2+−˜C 2−)B (m b )+1200MeV 2ps −1,(25)Γ(D ±)−Γ(D 0)=cos 4θc G 2F m 3c f 2D 3(C 2++C 2−)˜B (m c )∼−0.8 f DOn the contrary,inΩQ the two strange quarks form a J P=1+state,and a correlation between the spins of heavy and light quarks is present.The absence of spin correlation forthe heavy quark in the triplet of hyperons somewhat reduces the number of independentfour-quark operators,having nonvanishing diagonal matrix elements over these baryons. Indeed,the operators entering L(3)eff contain both vector and axial bilinear forms for the heavy quarks.However the axial part requires a correlation of the heavy quark spin withthat of a light quark,and is thus vanishing for the hyperons in the triplet.Therefore only the structures with vector currents are relevant for these hyperons.These structures are of thetype(qγµq)and(q kγµq i)with q being d,s or u.Theﬂavor SU(3)symmetrythen allows to express,for each of the two color combinations,the matrix elements of threediﬀerent operators,corresponding to threeﬂavors of q,over the baryons in the triplet interms of only two combinations:ﬂavor octet andﬂavor singlet.Thus all eﬀects of L(3)eff inthe triplet of the baryons can be expressed in terms of four independent combinations of matrix elements.These can be chosen in the following way:x= 1QγµQ)[(sγµs)] Ξ(d)Q−ΛQ= 1QγµQ) (dγµd) ΛQ−Ξ(u)Q,(27) y= 1Q iγµQ k)[(s kγµs i)] Ξ(d)Q−ΛQ= 1Q iγµQ k) (d kγµd i) ΛQ−Ξ(u)Q, with the notation for the diﬀerences of the matrix elements: O A−B= A|O|A − B|O|B ,for theﬂavor octet part and the matrix elements:x s=1QγµQ) (dγµd)+(3 H Q|(u kγµu i)+(s kγµs i)|H Q (28)for theﬂavor singlet part,where H Q stands for any heavy hyperon in the(anti)triplet.The initial,very approximate,theoretical estimates of the matrix elements[4]were es-sentially based on a non-relativistic constituent quark model,where these matrix elements are proportional to the density of a light quark at the location of the heavy one,i.e.in terms of the wave function,proportional to|ψ(0)|ing then the same picture for the matrix elements over pseudoscalar mesons,relating the quantity|ψ(0)|2to the annihilation constant f P,and assuming that|ψ(0)|2is approximately the same in baryons as in mesons, one arrived at the estimatey=−x=x s=−y s≈f2D M Dwhere the sign relation between x and y is inferred from the color antisymmetry of the constituent quark wave function for baryons.Since the constituent picture was believed to be valid at distances of the order of the hadron size,the estimate(29)was applied to the matrix elements in a low normalization point whereαs(µ)≈1.For the matrix elements of the operators,containing s quarks over theΩQ hyperon,this picture predicts an enhancement factor due to the spin correlation:ΩQ|(sΓµs)|ΩQ =− ΩQ|(s kΓµs i)|ΩQ =10[(C5−C3)x+(C6−C4)y],4πG2F m2cδnl,02≡Γnl∆S=∆C(Λc)−Γnl∆S=∆C(Ξ+c)=cos4θcdecays in the baryon triplet isδnl,1≡Γnl ∆S =0(Ξ0c )−Γnl ∆S =0(Λc )=cos 2θc sin 2θc G 2F m 2c12π[L 1x +L 2y ].(33)Finally,the Cabibbo suppressed semileptonic decay rates are equal for Λc and Ξ0c ,due to the ∆V =0property of the corresponding interaction.Thus the only diﬀerence for these isδsl,1≡Γsl ∆S =0(Λc )−Γsl ∆S =0(Ξ+c )=−sin 2θc G 2F m 2c4πcos 2θ x cos 2θ(C 5−C 3)+sin 2θ(2C 5−C 1−C 3)−23L 2,(35)and∆2=δnl,02−2δsl,0+2δsl,1=G 2F m 2c 3(cos 2θ−sin 2θ)L 1+y cos 4θ(C 4−C 2)+2m c2,(37)while the dependence of the thus extracted matrix element y on the normalization point µis shown in Fig.24.23456-0.04-0.020.02yxκFigure 2:The values of the extracted matrix elements x and y in GeV 3vs.the normalization point parameter κ=αs (µ)/αs (m c ).The thick lines correspond to the central value of the data on lifetimes of charmed baryons,and the thin lines show the error corridors.Theextracted values of x and y scale as m −2c with the assumed mass of the charmed quark,andthe plots are shown for m c =1.4GeV .Notably,the extracted values of x and y are in a drastic variance with the simplistic constituent model:the color antisymmetry relation,x =−y ,does not hold at any reasonable µ,and the absolute value of x is substantially enhanced 5Once the non-singlet matrix elements are determined,they can be used for predicting diﬀerences of other inclusive decay rates within the triplet of charmed hyperons as well as for the b baryons.Due to correlation of errors in x and y it makes more sense to express the predictions directly in terms of the total decay rates of the charmed hyperons.The thus arising relations between the rates do not depend on the normalization parameter µ.In this way one ﬁnds [28]for the diﬀerence of the Cabibbo dominant semileptonic decay rates between either of the Ξc hyperons and Λc :Γsl (Ξc )−Γsl (Λc )≈δsl,0=0.13∆1−0.065∆2≈0.59±0.32ps −1.(38)When compared with the data on the total semileptonic decay rate of Λc ,Γsl (Λc )=0.22±0.08ps −1,this prediction implies that the semileptonic decay rate of the charmed cascade hyperons can be 2–3times larger than that of Λc .The predictions found in a similar way for the inclusive Cabibbo suppressed decay ratesare[28]:for non-leptonic decaysδnl,1=0.082∆1+0.054∆2≈0.55±0.22ps−1(39) and for the semileptonic onesδsl,1=tan2θcδsl,0≈0.030±0.016ps−1.(40) For the only diﬀerence of the inclusive rates in the triplet of b baryons,Γ(Λb)−Γ(Ξ−b), oneﬁnds an expression in terms of x and y,or alternatively,in terms of the diﬀerences∆1 and∆2between the charmed hyperons,Γ(Λb)−Γ(Ξ−b)=cos2θc|V bc|2G2F m2bm2c(0.85∆1+0.91∆2)≈0.015∆1+0.016∆2≈0.11±0.03ps−1.(41) When compared with the data on the total decay rate ofΛb this result predicts about14% longer lifetime ofΞ−b than that ofΛb.The singlet matrix elements x s and y s(cf.eq.(28))are related to the shift of the average decay rate of the hyperons in the triplet:3 Γ(ΛQ)+Γ(Ξ1Q)+Γ(Ξ2Q) .(42) For the charmed baryons the shift of the dominant non-leptonic decay rate is given by[29]δ(3,0)nl8π(C 2++C2−)κ5/18(x s−3y s),(43)while for the b baryons the corresponding expression reads asδ(3)8π(˜C+−˜C−)2˜κ5/18(x s−3y s).(44) The combination x s−3y s of the SU(3)singlet matrix elements cancels in the ratio of the shifts for b hyperons and the charmed ones:δ(3)cos4m2bC2++C2− αs(m c)Γc≈0.0025δ(3,0)nl˜C)2/(C2++C2−),which parametrically is of the second order inαs,and numerically is only −about0.12.An estimate ofδ(3)Γc for charmed baryons.The latter shift can be conservatively bounded from aboveΓc=6.0±0.7ps−1,which then by the average total decay rate of those baryons:δ(3,0)nlyields,using eq.(45),an upper boundδ(3)Γc the contribution of the‘parton’term,which can be estimated from the decay rate of D0with account of the O(m−2c)eﬀects,as amounting to about3ps−1.(One should also take into account the semileptonic contribution to the total decay rates,which however is quite small at this level of accuracy).Thus a realistic evaluation ofδ(3)Γb due to the non-singlet operators is one third of the splitting(41),i.e.about5%.Adding to this the1%shift of the average width and another1%diﬀerence from the meson decays due to the suppression of the latter by the m−2b chromomagnetic eﬀects,one concludes that at the present level of theoretical understanding it looks impossible to explain a more than10%enhancement of the total decay rate ofΛb relative to B d,where an ample3%margin is added for the uncertainties of higher order terms in OPE as well as for higher order QCD radiative eﬀects in the discussed corrections. In other words,the expected pattern of the lifetimes of the b hyperons in the triplet,relative to B d,isτ(Ξ0b)≈τ(Λb)<τ(B d)<τ(Ξ−b),(46) with the“best”theoretical estimate of the diﬀerences to be about7%for each step of the inequality.For the double strange hyperonsΩc andΩb there is presently no better approach to evaluating the four-quark matrix elements,than the use of simplistic relations,like(30) based on constituent quark model.Such relations imply that the eﬀects of the strange quark,WS and PI,in theΩQ baryons are signiﬁcantly enhanced over the same eﬀects in the cascade hyperons.In charmed baryons a presence of strange spectator quark enhances the decay through positive interference with the quark emerging from the c→s transition in the decay.ForΩc this implies a signiﬁcant enhancement of the total decay rate[4],which is in perfect agreement with the data on theΩc lifetime.Also a similar enhancement is expected for the semileptonic decay rate ofΩc.In b baryons,on the contrary,the interference eﬀect。

科普书的英文作文怎么写

科普书的英文作文怎么写Science is amazing. It helps us understand the world around us and unravel the mysteries of the universe. From the tiniest particles to the vastness of space, science is constantly expanding our knowledge. It's like a never-ending adventure that keeps us curious and excited.Have you ever wondered how the Earth was formed? Well, billions of years ago, a cloud of gas and dust collapsed under its own gravity and formed our planet. It'sincredible to think that we are made up of the same elements that were present at the birth of the universe. We are all stardust!Speaking of elements, did you know that there are over 100 different ones? They make up everything we see and touch. From the oxygen we breathe to the iron in our blood, elements are the building blocks of life. It's fascinating how they combine and interact to create the world as we know it.Let's talk about animals now. Did you know that some animals can regenerate their body parts? Take the starfish, for example. If it loses an arm, it can grow a new one.Isn't that incredible? Imagine if humans had that ability. We could regrow limbs and heal ourselves in a matter of weeks. Science is constantly studying these amazingabilities and trying to unlock their secrets.Now, let's dive into the world of medicine. Have you ever heard of antibiotics? They are powerful drugs that can kill bacteria and cure infections. Before their discovery, a simple cut could lead to a deadly infection. Thanks to science, we now have the means to fight off these harmful bacteria and save lives. It's truly a medical breakthrough.Speaking of breakthroughs, have you heard of the CRISPR gene-editing technology? It's like something out of a science fiction movie. Scientists can now edit genes and potentially cure genetic diseases. Imagine a world where we can eradicate diseases like cancer or Alzheimer's. It may seem like a distant dream, but science is making incredibleprogress every day.In conclusion, science is a never-ending journey of discovery. It's a way for us to understand the world and push the boundaries of what is possible. From the formation of our planet to the mysteries of the human body, science is always there, guiding us forward. So, let's embrace the wonders of science and continue to explore, learn, and be amazed.。

Study of three-body charmless B decays at Belle

a rXiv:h ep-e x /1751v12Jul21BELLE-CONF-0114Study of three-body charmless B decays at Belle The Belle Collaboration Abstract Using a data sample of 21.3fb −1collected by the Belle detector,three body charmless decays B +→K +h +h −have been studied.With no as-sumptions on the intermediate mechanisms,the following branching frac-tions have been measured for the ﬁrst time B (B +→K +π−π+)=(58.5±7.1±8.8)×10−6and B (B +→K +K −K +)=(37.0±3.9±4.4)×10−6.We also present the ﬁrst observations of the decay mode B +→K ∗0(892)π+with a branching fraction of B (B +→K ∗0(892)π+)=(16.7+3.7+2.1+3.0−3.4−2.1−5.9)×10−6and the decay mode B +→f 0(980)K +with a product branching fraction of B (B +→f 0(980)K +)×B (f 0(980)→π+π−)=(11.7+2.5+1.5+4.1−2.7−1.5−1.0)×10−6.Typeset using REVT E XK.Abe9,K.Abe37,R.Abe27,I.Adachi9,Byoung Sup Ahn16,H.Aihara39,M.Akatsu20, K.Asai21,M.Asai10,Y.Asano44,T.Aso43,V.Aulchenko2,T.Aushev14,A.M.Bakich35,E.Banas25,S.Behari9,P.K.Behera45,D.Beiline2,A.Bondar2,A.Bozek25,T.E.Browder8,B.C.K.Casey8,P.Chang24,Y.Chao24,K.-F.Chen24,B.G.Cheon34, R.Chistov14,S.-K.Choi7,Y.Choi34,L.Y.Dong12,J.Dragic19,A.Drutskoy14,S.Eidelman2,V.Eiges14,Y.Enari20,C.W.Everton19,F.Fang8,H.Fujii9,C.Fukunaga41, M.Fukushima11,N.Gabyshev9,A.Garmash2,9,T.J.Gershon9,A.Gordon19,K.Gotow46,H.Guler8,R.Guo22,J.Haba9,H.Hamasaki9,K.Hanagaki31,F.Handa38,K.Hara29, T.Hara29,N.C.Hastings19,H.Hayashii21,M.Hazumi29,E.M.Heenan19,Y.Higasino20, I.Higuchi38,T.Higuchi39,T.Hirai40,H.Hirano42,T.Hojo29,T.Hokuue20,Y.Hoshi37,K.Hoshina42,S.R.Hou24,W.-S.Hou24,S.-C.Hsu24,H.-C.Huang24,Y.Igarashi9, T.Iijima9,H.Ikeda9,K.Ikeda21,K.Inami20,A.Ishikawa20,H.Ishino40,R.Itoh9, G.Iwai27,H.Iwasaki9,Y.Iwasaki9,D.J.Jackson29,P.Jalocha25,H.K.Jang33,M.Jones8,R.Kagan14,H.Kakuno40,J.Kaneko40,J.H.Kang48,J.S.Kang16,P.Kapusta25, N.Katayama9,H.Kawai3,H.Kawai39,Y.Kawakami20,N.Kawamura1,T.Kawasaki27, H.Kichimi9,D.W.Kim34,Heejong Kim48,H.J.Kim48,Hyunwoo Kim16,S.K.Kim33, T.H.Kim48,K.Kinoshita5,S.Kobayashi32,S.Koishi40,H.Konishi42,K.Korotushenko31, P.Krokovny2,R.Kulasiri5,S.Kumar30,T.Kuniya32,E.Kurihara3,A.Kuzmin2, Y.-J.Kwon48,nge6,G.Leder13,S.H.Lee33,C.Leonidopoulos31,Y.-S.Lin24, D.Liventsev14,R.-S.Lu24,J.MacNaughton13,D.Marlow31,T.Matsubara39,S.Matsui20,S.Matsumoto4,T.Matsumoto20,Y.Mikami38,K.Misono20,K.Miyabayashi21,H.Miyake29,H.Miyata27,L.C.Moﬃtt19,G.R.Moloney19,G.F.Moorhead19,S.Mori44, T.Mori4,A.Murakami32,T.Nagamine38,Y.Nagasaka10,Y.Nagashima29,T.Nakadaira39, T.Nakamura40,E.Nakano28,M.Nakao9,H.Nakazawa4,J.W.Nam34,Z.Natkaniec25, K.Neichi37,S.Nishida17,O.Nitoh42,S.Noguchi21,T.Nozaki9,S.Ogawa36,T.Ohshima20, Y.Ohshima40,T.Okabe20,T.Okazaki21,S.Okuno15,S.L.Olsen8,H.Ozaki9,P.Pakhlov14,H.Palka25,C.S.Park33,C.W.Park16,H.Park18,L.S.Peak35,M.Peters8, L.E.Piilonen46,E.Prebys31,J.L.Rodriguez8,N.Root2,M.Rozanska25,K.Rybicki25, J.Ryuko29,H.Sagawa9,Y.Sakai9,H.Sakamoto17,M.Satapathy45,A.Satpathy9,5,S.Schrenk5,S.Semenov14,K.Senyo20,Y.Settai4,M.E.Sevior19,H.Shibuya36,B.Shwartz2,A.Sidorov2,S.Staniˇc44,A.Sugi20,A.Sugiyama20,K.Sumisawa9,T.Sumiyoshi9,J.-I.Suzuki9,K.Suzuki3,S.Suzuki47,S.Y.Suzuki9,S.K.Swain8,H.Tajima39,T.Takahashi28,F.Takasaki9,M.Takita29,K.Tamai9,N.Tamura27,J.Tanaka39,M.Tanaka9,G.N.Taylor19,Y.Teramoto28,M.Tomoto9,T.Tomura39, S.N.Tovey19,K.Trabelsi8,T.Tsuboyama9,T.Tsukamoto9,S.Uehara9,K.Ueno24, Y.Unno3,S.Uno9,hiroda9,S.E.Vahsen31,K.E.Varvell35,C.C.Wang24,C.H.Wang23,J.G.Wang46,M.-Z.Wang24,Y.Watanabe40,E.Won33,B.D.Yabsley9,Y.Yamada9,M.Yamaga38,A.Yamaguchi38,H.Yamamoto8,T.Yamanaka29,Y.Yamashita26,M.Yamauchi9,S.Yanaka40,J.Yashima9,M.Yokoyama39,K.Yoshida20, Y.Yusa38,H.Yuta1,C.C.Zhang12,J.Zhang44,H.W.Zhao9,Y.Zheng8,V.Zhilich2,andD.ˇZontar441Aomori University,Aomori2Budker Institute of Nuclear Physics,Novosibirsk3Chiba University,Chiba4Chuo University,Tokyo5University of Cincinnati,Cincinnati OH6University of Frankfurt,Frankfurt7Gyeongsang National University,Chinju8University of Hawaii,Honolulu HI9High Energy Accelerator Research Organization(KEK),Tsukuba 10Hiroshima Institute of Technology,Hiroshima 11Institute for Cosmic Ray Research,University of Tokyo,Tokyo12Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 13Institute of High Energy Physics,Vienna14Institute for Theoretical and Experimental Physics,Moscow15Kanagawa University,Yokohama16Korea University,Seoul17Kyoto University,Kyoto18Kyungpook National University,Taegu19University of Melbourne,Victoria20Nagoya University,Nagoya21Nara Women’s University,Nara22National Kaohsiung Normal University,Kaohsiung23National Lien-Ho Institute of Technology,Miao Li24National Taiwan University,Taipei25H.Niewodniczanski Institute of Nuclear Physics,Krakow26Nihon Dental College,Niigata27Niigata University,Niigata28Osaka City University,Osaka29Osaka University,Osaka30Panjab University,Chandigarh31Princeton University,Princeton NJ32Saga University,Saga33Seoul National University,Seoul34Sungkyunkwan University,Suwon35University of Sydney,Sydney NSW36Toho University,Funabashi37Tohoku Gakuin University,Tagajo38Tohoku University,Sendai39University of Tokyo,Tokyo40Tokyo Institute of Technology,Tokyo41Tokyo Metropolitan University,Tokyo42Tokyo University of Agriculture and Technology,Tokyo43Toyama National College of Maritime Technology,Toyama44University of Tsukuba,Tsukuba45Utkal University,Bhubaneswer46Virginia Polytechnic Institute and State University,Blacksburg VA47Yokkaichi University,Yokkaichi48Yonsei University,SeoulI.INTRODUCTIONDuring the last few years,a considerable amount of new information on charmless hadronic decays of B-mesons has been reported,primarily by the CLEO Collaboration.The discoveries of the B→Kπand B→ππdecay modes[1]have provided a real basis forsearches for direct-CP violating eﬀects in the B-meson system.However,because of large combinatoric backgrounds,studies of charmless B decays haveconcentrated mainly on two-body decay processes.In this paper,we report the results of a study of decays B+→K+h+h−(h stands for a charged pion or kaon)where no assumptions are made about intermediate hadronic resonances.The inclusion of charge conjugate statesis implicit throughout this report unless explicitly stated otherwise.The data sample used for this analysis consists of21.3fb−1taken at theΥ(4S)(on-resonance)and2.3fb−1taken60MeV below for continuum studies(oﬀ-resonance).The data were collected with the Belle detector[2]operating at the KEKB asymmetric energy e+e−collider[3].II.THE BELLE DETECTORBelle is large-solid-angle spectrometer based on a1.5Tesla superconducting solenoid magnet.Charged particle tracking is provided by a silicon vertex detector(SVD)and a cylindrical drift chamber(CDC)that surround the interaction region.The SVD consists of three approximately cylindrical layers of double-sided silicon strip detectors;one side of each detector measures the z coordinate and the other the r-φcoordinate.The CDC has 50cylindrical layers of anode wires;the inner three layers have instrumented cathodes for z coordinate measurements[4].Twenty of the wire layers are inclined at small angles to provide small-angle stereo measurements of z coordinates along the particle trajectories. The charged particle acceptance covers the laboratory polar angle betweenθ=17◦and150◦corresponding to about92%of the full solid angle in the CMS.Tracks areﬁt using an incremental Kalmanﬁltering technique,where individual mea-surements found by the CDC pattern recognition algorithm are added successively to update the track’s parameters and covariance matrix at each measurement surface.This approach to trackﬁtting minimizes the eﬀects of multiple Coulomb scattering on the determination of the track parameters.Hits from the SVD are associated and included during the last steps of this recursion.The momentum resolution is determined from cosmic rays and e+e−→µ+µ−events to beσp t/p t=(0.30⊕0.19p t)%,where p t is the transverse momentum in GeV/c.Charged hadron identiﬁcation is provided by dE/dx measurements in the CDC,a mo-saic of1188aerogelˇCerenkov counters(ACC),and a barrel-like array of128time-of-ﬂight scintillation counters(TOF).The dE/dx measurements have a resolution for hadron tracks of6.9%and are useful forπ/K separation for p lab<0.8GeV/c and p lab>2.5GeV/c where p lab is the laboratory momentum.The TOF system has a time resolution for hadrons thatis σ≃100ps and provides π/K separation for p lab <1.5GeV/c [5].The indices of refrac-tion of the ACC elements vary with polar angle to match the kinematics of the asymmetric energy environment of Belle and cover the range 1.5<p lab <3.5GeV/c [6].Hadron identiﬁcation is accomplished by combining the information from these three subsystems into a single number using the likelihood method:L (h )=L ACC (h )×L T OF (h )×L CDC (h ),where h stands for the hadron type (π,K ,p ).High momentum tagged kaons and pions from kinematically selected D ∗+→D 0π+;D 0→K −π+decays are used to determine a charged particle identiﬁcation eﬃciency of about 90%and a misidentiﬁcation probability of about 8%.Electromagnetic showering particles are detected in an array of 8736CsI(Tl)crystals located in the magnetic volume and covering the same solid angle as the charged particle tracking system [7].The energy resolution for electromagnetic showers is σE /E =(1.3⊕0.07/E ⊕0.8/E 1/4)%,(E in GeV).Neutral pions are detected via their π0→γγdecay.The π0mass resolution varies slowly with energy,averaging σm π0=4.9MeV.Electron identiﬁcation in Belle is based on a combination of dE/dx measurements in the CDC,the response of the ACC,and the position,shape and total energy (i.e.E/p )of the shower registered in the CsI calorimeter.The electron identiﬁcation eﬃciency,determined by embedding Monte Carlo tracks in multihadron data,is greater than 92%for tracks with p lab >1.0GeV/c and the hadron misidentiﬁcation probability,determined from K S →π+π−decays,is below 0.3%.The 1.5T magnetic ﬁeld is returned via an iron yoke that is instrumented to detect muons and K L mesons.This detection system,called the KLM,consists of alternating layers of charged particle detectors and 4.7cm thick steel plates.The total steel thickness of 65.8cm plus the material of the inner detector corresponds to 4.7nuclear interaction lengths at normal incidence.The system covers polar angles between θ=20◦and 155◦and the overall muon identiﬁcation eﬃciency,determined by a track embedding study similar to that used in the electron case,is greater than 87%for tracks reconstructed in the CDC with p lab >1.0GeV/c .The corresponding pion misidentiﬁcation probability determined from K S →π+π−decays is less than 2%.III.EVENT SELECTIONCharged tracks are required to satisfy a set of track quality cuts based on the average hit residual and the impact parameters in both the r -φand r -z planes.We require that the transverse track momenta be greater than 100MeV/c to reduce low momentum combinatoric background.All the cuts used for the selection of charged tracks are listed in Table I.Charged particles are identiﬁed as K ’s or π’s by cutting on the likelihood ratio (PID):P ID (K )=L (K )L (π)+L (K )=1−P ID (K )At large momenta (>2.5GeV/c )only the ACC and dE/dx are used since here the TOF provides no signiﬁcant separation of kaons and pions.For all three-body ﬁnal states exceptTABLE I.Parameters used for selection of charged tracks.Parameter Cut valueL(p)+L(K)<0.95The candidate events are identiﬁed by using the beam-constrained mass M BC= s/2,where E∗B and P∗B are the measured√energy and3-momentum of the B candidate in theΥ(4S)rest frame and1−x2exp[−ξ(1−x2)],where x= M B/E∗beam andξis a freeﬁt parameter.The∆E signal shape is parameterized by the sum of two Gaussians with the same mean. The shape of the background in the∆E distribution from non-resonant e+e−→q¯q(q= u,d,s,c)continuum events is parameterized by aﬁrst order polynomial.The∆E shape due to background from other B and¯B decay processes has a substantial dependence on the ﬁnal state being studied.Unless explicitly stated otherwise,the contributions from these backgrounds are also parameterized by aﬁrst order polynomial.In the following,we refer to the“B signal region;”this is deﬁned as:5.272<M BC<5.289GeV/c2;|∆E|<40MeV.IV.BACKGROUND SUPPRESSIONAn important issue for this analysis is the suppression of the large combinatoric back-ground that is dominated by q¯q continuum events.To suppress this background,we use a set of variables that characterize the event topology.Since the two B mesons produced from theΥ(4S)decay are nearly at rest in the CMS frame,the angles of the decay products of two B’s are uncorrelated and the events tend to be spherical.In contrast,hadrons from continuum q¯q events tend to exhibit a two-jet structure.Figure1a shows distributions of|cos(θT hr)|,whereθT hr is the angle between the thrust axis of the B candidate and that of the rest of the event.The distribution is strongly peaked near|cos(θT hr)|≃1.0for q¯q events while it is nearlyﬂat for B¯B events.We require |cos(θT hr)|<0.80for all modes under consideration;this eliminates83%of the continuum background and retains79%of the signal events.After the imposition of the cos(θT hr),q¯q and B¯B requirements,the remaining events still have some diﬀerences in topology that are exploited for further continuum suppression.We construct a“Virtual Calorimeter”[9]by dividing the space around the candidate thrust axis into nine polar angle intervals of10◦each;the i-th interval covers angles from(i-1)×10◦to i×10◦.We deﬁne the momentumﬂows,x i(i=1,9),into the i-th interval as a scalar sum of the momenta of all charged tracks and neutral showers directed in that interval.The momentumﬂow in corresponding forward and backward intervals are combined.Angular momentum conservation provides some additional discrimination between B¯B and continuum q¯q events.In q¯q production,the direction of the candidate thrust axis,θT,with respect to the beam axis in the cms frame tends to maintain the1+cos2(θT) distribution of the primary quarks.The direction of the B candidate thrust axis for B¯B events is uniform.The B candidate direction,θB,with respect to the beam axis exhibits a sin2(θB)distribution for B¯B events and is uniform for q¯q events.A Fisher discriminant[10]is formed from11variables:the nine variables of the“Virtual Calorimeter”,|cos(θT)|,and|cos(θB)|.The discriminant F is the linear combinationF=11 i=1αi x iof the input variables,x i,that maximizes the separation between signal and background. The coeﬃcientsαi are determined from the Monte Carlo simulation using a large set of continuum events and signal events modeled as B+→K+π+π−.We use the same set of coeﬃcientsαi for all modes under study.Figure1b shows the F distributions for the Monte Carlo signal in the mode B+→K+π+π−,and the data signal in the mode B+→¯D0π+ followed by¯D0→K+π−.The F distributions for Monte Carlo background and below-threshold background data for modes comprising three charged tracks are also presented in Fig.1b.The F distributions for both the signal and background areﬁtted to Gaussian func-tions.The separation between the mean values of the signal and background distributions is approximately1.3times the signal width.For the Kππand KKπﬁnal states we make the requirement on the Fisher discriminant variable F>0.8;this rejects90%of continuum background with about54%eﬃciency for the signal.In case of the KKKﬁnal states,the continuum background is much smaller and we make the looser requirement F>0.This rejects53%of continuum background with about89%eﬃciency for the signal.To determine the dominant sources of background from other B-meson decay modes we use a large set of Monte Carlo generated B¯B events where both B mesons decay generically. Most of the B¯B related background is found to originate from B+→¯D0π+and B+→J/ψ(ψ(2S))K+decays.To suppress this type of background we apply the requirements oninvariant masses of two-particle combinations that are described below.The backgroundfrom the B semileptonic decays is additionally suppressed by the electron veto requirement. The most signiﬁcant background to K+π+π−ﬁnal state from the B rare decays is found tooriginate from the B+→η′K+followed byη′→ρ0γ.We expect about3%of the events of this type to satisfy all the selection criteria.Weﬁnd no signiﬁcant background to theK+K+K−ﬁnal state from other rare decays of B mesons.V.RESULTS OF THE ANALYSISA.B+→K+π+π−For the K+π+π−ﬁnal state,we select B candidates formed from three charged tracks where one track is positively identiﬁed as a kaon and the other two tracks are consistent with the pion hypothesis.The resulting two dimensional∆E versus M BC plot for all selected K+π+π−combinations is presented in Fig.2a where the B signal region is inside the box. Figure2b shows the Dalitz plot for candidates in the B signal rge contributions from B+→¯D0π+where¯D0→K+π−and B+→J/ψ(ψ(2S))K+where J/ψ(ψ(2S))→µ+µ−are apparent in the Dalitz plot.Modes with J/ψ(ψ(2S))contribute to thisﬁnal state due to the muon-pion misidentiﬁcation.The contribution from the J/ψ(ψ(2S))→e+e−submode is found to be negligible(less than0.5%)after the electron veto requirement.For further analysis we exclude¯D0and J/ψ(ψ(2S))signals by imposing requirements on the invariant masses of two intermediate particles:|M(K+π−)−1.865|>0.100GeV/c2;|M(h+h−)−3.097|>0.070GeV/c2;|M(h+h−)−3.686|>0.050GeV/c2, where h+and h−are pion candidates.For the J/ψ(ψ(2S))rejection,we use the muon mass hypothesis for charged tracks to calculate M(h+h−).The∆E and M BC distributions for the events remaining after the exclusion of these largesignals are presented in Fig.3a and Fig.3b,respectively.Here a signiﬁcant enhancement in the B signal region is still observed;the results of aﬁt to this∆E distribution are presented in Table IV.The expected∆E and M BC distributions,which are the sum of luminosity-scaled oﬀ-resonance data and B¯B Monte Carlo,are shown as open histograms in Figs.3a and3b,respectively;the contributions from only the B¯B Monte Carlo sample are shown as hatched histograms.In the∆E spectrum,the shape of the B¯B background component is approximated as an exponential function with a parameter determined from the B¯B Monte Carlo.As can be seen from the hatched histograms in Figs.3a and3b,there is no signiﬁcant contribution to the signal from B¯B generic decays after the large known backgrounds have been removed.To examine possible intermediate two-body states in the observed B+→K+π+π−signal, we analyze the K+π−andπ+π−invariant mass spectra shown in Figs.4a and4b,respec-tively.To suppress the feed-across between theπ+π−and K+π−states we require the K+π−(π+π−)invariant mass to be larger than2.0(1.5)GeV/c2when making theπ+π−(K+π−) projection.The hatched histograms shown in Figs.4a and4b are the h+h−invariant mass spectra for background events in the∆E sidebands:5.272<M BC<5.289GeV/c2and−0.080<∆E<−0.050or0.050<∆E<0.150GeV,scaled by area.The K+π−invariant mass spectrum is characterized by a narrow peak around0.9GeV/c2 which is identiﬁed as K∗0(892)and a broad enhancement above1.0GeV/c2which is subse-quently referred to as K X(1400).In theπ+π−invariant mass spectrum two distinct structures in the low mass region are observed.One is slightly below1.0GeV/c2which is identiﬁed as f0(980)and the other between1.0GeV/c2and1.5GeV/c2and referred to as f X(1300).The peak around3.4GeV/c2is consistent with the process B+→χc0K+,χc0→π+π−,and is the subject ofa diﬀerent analysis[11].In this paper we exclude theχc0candidates from the analysis of two-bodyﬁnal states by applying the requirement on theπ+π−invariant mass:|M(π+π−)−3.415|>0.050GeV/c2.For further analysis we subdivide the Dalitz plot area into seven non-overlapping regions as deﬁned in Table II.Regions from I to V are arranged to contain the major part of the signal from the B+→K∗0(892)π+,B+→K X(1400)π+,B+→ρ0(770)K+,B+→f0(980)K+,and B+→f X(1300)K+ﬁnal states,respectively.The area in the Dalitz plot where Kπandππresonances overlap is covered by the region VI,and region VII covers the rest of the Dalitz plot.The∆E and M BC distributions for each region are shown in Fig.5and the results of theﬁts are summarized in Table II.As can be seen from Fig.5and Table II,the contribution from region VII to the total number of signal events is negligibly small.TABLE II.Results of theﬁt to the∆E distribution for diﬀerent regions in the K+π+π−Dalitz plot.Columns list the deﬁnition of each region,reconstruction eﬃciency from Monte Carlo simulation,signal yield and statistical signiﬁcance.Region Mass range,GeV/c2Eﬃciency,%Yield,event Signiﬁcance,σFigure6a shows the two-dimensional∆E versus M BC plot for all selected K+K+K−combinations and Fig.6b shows the Dalitz plot for candidate events in the B signal region. Since in this case there are two same-charge kaons,we distinguish the K+K−combinations with smaller,M(K+K−)min,and larger,M(K+K−)max,invariant masses.We avoid double entries by forming the Dalitz plot as M2(K+K−)max versus M2(K+K−)min,as shown in Fig.6b.The signal from the Cabibbo-suppressed B+→D0CP K+,D0CP→K+K−decay mode is apparent as a vertical strip in the Fig.6b Dalitz plot.The notation D0CP means that the D meson decays to the CP eigenstate.The corresponding Cabibbo-allowed B+→D0CPπ+,D0CP→K+K−decays can also contribute to thisﬁnal state as a result of pion-kaon misidentiﬁcation.The detailed analysis of the decays of type B+→D0CP K+is described in ref.[12].We exclude candidates consistent with the B+→D0CP h+,D0CP→K+K−hypothesis from further analysis by imposing the requirement on the K+K−invariant mass:|M(K+K−)−1.865|>0.025GeV/c2.The∆E and M BC distributions after the exclusion of D mesons are presented in Figs.7a and7b,respectively.A large peak in the B signal region is apparent in both distributions. The results of aﬁt to the∆E distribution are presented in Table IV.The open histograms in Figs.8a and8b show the M(K+K−)min and M(K+K−)max dis-tributions for selected events,respectively;the hatched histograms show the corresponding spectra for the∆E sidebands:5.272<M BC<5.289GeV/c2and−0.200<∆E<−0.050or0.050<∆E<0.200GeV,scaled by area.The M(K+K−)min spectrum,Fig.8a,is characterized by a narrow peak at 1.02GeV/c2corresponding to theφ(1020)meson and a broad structure around1.5GeV/c2, which is subsequently referred to as f X(1500).To exclude the possible contribution from the B+→χc0K+,χc0→K+K−ﬁnal state we apply the requirement on the K+K−invariant mass:|M(K+K−)−3.415|>0.050GeV/c2.The study of thisﬁnal state is described in ref.[11].For further analysis we subdivide the area of the Dalitz plot into the four non-overlapping regions deﬁned in Table III.Regions I and II are arranged to contain the major part of the signal from the B+→φ(1020)K+and B+→f X(1500)K+ﬁnal states respectively.Regions III and IV cover the rest part of the Dalitz plot.The∆E and M BC distributions for each region are shown in Fig.9and the results of theﬁt are summarized in Table III.VI.BRANCHING FRACTIONS RESULTSTo determine branching fractions we normalize our results to the observed B+→¯D0π,¯D0→K+π−signal.Although this introduces a9.7%systematic error due to the uncertainty in the B+→¯D0πbranching fraction,it removes systematic eﬀects in the particle identiﬁ-cation eﬃciency,charged track reconstruction eﬃciency and the systematic uncertainty due to the cuts on event shape variables.TABLE III.Results of theﬁt to the∆E distribution for diﬀerent regions in the K+K+K−Dalitz plot.Columns list the deﬁnition of each region,reconstruction eﬃciency from Monte Carlo simulation,signal yield and statistical signiﬁcance.Region Mass range,GeV/c2Eﬃciency,%Yield,event Signiﬁcance,σεDπN Dπ×TABLE IV.Measurement results.Branching fractions and90% C.L.upper limits for B+→K+h+h−ﬁnal states.Mode Eﬃciency,%Yield,event B,10−6εij matrix is determined from a Monte Carlo simulation and includes the reconstruction eﬃciency.This procedure takes correlations between diﬀerent channels into account when determining the statistical errors.The results of theﬁt are summarized in Table bining all the relevant numbers and using Eq.1,we calculate the product of branching fractions B(B+→Rh+)×B(R→h+h−), where R denotes the two-body intermediate resonant state.The branching fraction result for the B+→K∗0(892)π+ﬁnal state is in agreement with the results of a separate study of B meson decays to the pseudo-scalar and vectorﬁnal states[14].We present three types of error for the branching fractions:theﬁrst error is statistical,the second is systematic,and the third reﬂects the model-dependent uncertainty.In general, the model-dependent error is due to uncertainties in the eﬀects of interference between diﬀerent resonant states.We estimate this error by means of a B+→K+π+π−Monte Carlo simulation that includes interference eﬀects between allﬁnal states mentioned above. We vary the relative phases of resonances and determine the signal yield using the procedure described above.The maximal deviations from the central values are used as an estimate of the model dependence of the obtained branching fractions.TABLE V.Results of the simultaneousﬁt to the K+π+π−ﬁnal state.Two body mode Eﬃciency,%Yield,events Signiﬁcance,σB B+→Rh+×B R→h+h−,10−6Then we extract the signal yield for the two-bodyﬁnal states:B+→φ(1020)K+and the so-called B+→f X(1500)K+,which is,in fact,all of the remaining signal.We follow the same procedure as we used for the K+π+π−ﬁnal state.The signal yields are determined from a simultaneousﬁt to the∆E distributions for four separate regions of the K+K+K−Dalitz plot(see Fig.9and Table III).The results of theﬁt are summarized in Table VI.The branching fraction result for the B+→φ(1020)K+ﬁnal state is in good agreement with the results of a dedicated analysis of the B+→φ(1020)K+and B+→φ(1020)K∗+(892)ﬁnal states[15],B(B+→φ(1020)K+)=(10.6+2.1−1.9±2.2)×10−6.This latter number should be considered as the current“oﬃcial”Belle result for the B+→φ(1020)K+branching fraction.TABLE VI.Results of the simultaneousﬁt for the K+K+K−ﬁnal state.Two body mode Eﬃciency,%Yield,events Signiﬁcance,σB B+→RK+×B R→K+K−,10−6to as K X(1400))agrees with the scalar K∗0(1430)hypothesis.This is also in agreement with theoretical predictions[19,20]for the B+→K∗0(1430)π+branching fraction made based on the factorization model.Nevertheless,we cannot exclude some contribution from the tensor K∗2(1430)state.Large uncertainties arise in the interpretation of the peak with aπ+π−invariant mass around1300MeV/c2in the Kππsystem.There are two known candidate states:the f2(1270)and f0(1370)[13].Attributing the peak to the f0(1370),with its rather small coupling toπ+π−[21],would lead to an unusually large branching fraction for a charmless B decay mode.On the other hand,as recently shown in[22],factorization model predicts a very small branching ratio for B+→f2(1270)K+.If our observation is,in fact,due to the f2(1270),this would provide evidence for a signiﬁcant nonfactorizable contribution.We cannot identify the broad structure observed in the B+→K+K+K−ﬁnal state above φ(1020)meson.It is hardly compatible with the presence of single scalar state either f0(1370) and f0(1500)[13].We also cannot exclude the presence of a non-resonant contribution or the case of several resonances contributing to the excess in the K+K−invariant mass spectrum seen around1.5GeV/c2.Weﬁnd that eﬀects of interference between diﬀerent two-body intermediate states can have a signiﬁcant inﬂuence on the observed two-particle mass spectra and a full amplitude analysis of three-body B meson decays is required for a more complete understanding.This will be possible with increased statistics.ACKNOWLEDGEMENTWe wish to thank the KEKB accelerator group for the excellent operation of the KEKB accelerator.We acknowledge support from the Ministry of Education,Culture,Sports, Science,and Technology of Japan and the Japan Society for the Promotion of Science; the Australian Research Council and the Australian Department of Industry,Science and Resources;the Department of Science and Technology of India;the BK21program of the Ministry of Education of Korea and the CHEP SRC program of the Korea Science and Engineering Foundation;the Polish State Committee for Scientiﬁc Research under contract No.2P03B17017;the Ministry of Science and Technology of Russian Federation;the National Science Council and the Ministry of Education of Taiwan;the Japan-Taiwan Cooperative Program of the Interchange Association;and the U.S.Department of Energy.。

新视野大学英语第三版第二册Unit2课文原文+翻译

Unit 2The humanities: Out of date?1When the going gets tough, the tough take accounting.When the job market worsens, many students calculate they can't major in English or history.They have to study something that boosts their prospects of landing a job.2The data show that as students have increasingly shouldered the ever-rising cost of tuition, they have defected from the study of the humanities and toward applied science and "hard" skills that they bet will lead to employment.In other words, a college education is more and more seen as a means for economic betterment rather than a means for human betterment.This is a trend that is likely to persist and even accelerate.3Over the next few years, as labor markets struggle, the humanities will probably continue their long slide in succession.There already has been a nearly 50 percent decline in the portion of liberal arts majors over the past generation, and it is logical to think that the trend is bound to continue or even accelerate.Once the dominant pillars of university life, the humanities now play little roles when students take their college tours.These days, labs are more vivid and compelling than libraries.4Here, please allow me to stand up for and promote the true value that the humanities add to people's lives.Since ancient times, people have speculated about the mystery of those inner forces that drive some people to greatness and others to self-destruction. This inner drive has been called many things over the centuries.The famous psychologist,Sigmund Freud, called it the "unconscious mind" or, more familiarly, "instinct".5From the beginning of time, this inner aspect of our being, this drive that can be constructive or destructive, has captured our imagination.The stories of this amazing struggle have formed the basis of cultures the world over.Historians,architects, authors, philosophers and artists have captured the words, images and meanings of this inner struggle in the form of story, music, myth, painting, architecture, sculpture,landscape and traditions.These men and women developed artistic "languages" that help us understand these aspirations and also educate generations.This fertile body of work from ancient times, the very foundation of civilization, forms the basis of study of the humanities.6Studying the humanities improves our ability to read and write.No matter what we do in life, we will have a huge advantage if we can read complex ideas and understand their meaning.We will have a bright career if we are the person in the office who can write a clear and elegant analysis of those ideas!7Studying the humanities makes us familiar with the language of emotion and the creative process.In an information economy, many people have the ability to produce a useful product such as a new MP3 player.Yet, very few people have the ability to create a spectacular brand: the iPod.Most importantly, studying thehumanities invests us with great insight and self-awareness,there by releasing our creative energy and talent in a positive and constructive manner.8Perhaps the best argument in favor of the humanities is the scope of possibilities that are widely open to us.Did you know that James Cameron, world-famous director of the movie,Titanic, graduated with a degree in the humanities?So did Sally Ride, the first woman in space.So did actors Bruce Lee,Gwyneth Paltrow,Renee Zellweger and Matt Damon.Dr.Harold Varmus, who won a Nobel Prize for Medicine, studied the humanities.Even Michael Eisner, Chairman of the Disney Company, majored in the humanities. Famous people who studied the humanities make a long list indeed.It's easy to see that the humanities can prepare us for many different careers and jobs we can undertake, whether medicine, business, science or entertainment.If we study only mathematics, it's likely we will be a candidate only for jobs as a mathematician.If we include studying the humanities, we can make breakthroughs on many barriers and are limited only by our effort and imagination.9Of course, nowadays, if we study the humanities alone, we are liable to miss many opportunities.Each one of us needs to become as technically and professionally skilled as possible to help meet the needs of modern life.In fact, increasingly a pairing of technical knowledge and inner insight is seen as the ideal in the establishment of a career.If I were the Dean of Admissions at a medical school and two people applied to our school, both having the required basic scientific courses, one a philosophy major and the other solely a pre-med student, the philosophy applicant would be chosen.10In summary, the humanities help to create well-rounded human beings with insight and understanding of the passions, hopes and dreams common to all humanity.The humanities, the ancient timeless reservoir of knowledge, teach us to see things differently and broaden our horizons.They are as useful and relevant in our modern age as they have always been.Doesn't it make sense to spend some time in the company of the humanities, our outstanding and remarkable treasure of knowledge?Who knows how famous YOU might become!Translation人文学科：过时了吗？1 当形势变得困难时，强者会去选学会计。

新视野第三版读写教程第二册U7课后题答案

Un it 7 -Section ALanguage Focus - Words in Use1. It was esse ntial to (har ness) scie nee and tech no logy, not just for the economybut for environmen tal protect ion as well.2. Lan guage is the (symbolic) represe ntati on of a people, and it comb ines their historical and cultural backgrounds, as well as their approach to life.3. Because of the effective and helpful method, I was (disposed) to answer all the questions I could, and I never worried about making mistakes.4. It can be inferred from the passage that the commercial prosperity in Cambridge is due to hi-tech IT compa nies whose bus in ess has bee n (flourish ing).5. You will n eed to prove that the no ise (violated) the regulati ons, that yourn eighbor was caus ing the no ise, and that you attempted to have him stop.6. Most uni versities will guara ntee your (accommodati on) , at least duri ng yourfirst year, but you are likely to share a kitchen and bathroom with other students.7. Wemay (infer) from the report that hackers from outside of the company present a more serious threat to their security systems.8. She frowned at the bus in ess report, maki ng an effort to (compose) herself before she talked to the employees at the upco ming meeti ng.9. A crucial factor is that one wit ness' evide nee, though (plausible) , may be rejected because it is con tradicted by ano ther wit ness whose evide nee is already proved correct.10. Windsor Middle School has been famous for zero (toleranee) to violence and emphasis on respect for its stude nts and rules.Word Buildi ng1. fate2. horiz on3. mecha nic4. occasi on5. proport ion6. logical7. deny8. commercial9. relative10. prior11. con ti nue12. actual1. fatal2. horiz on tal3. mecha ni cal4. occasi onal5. proport ional6. logic7. denial8. commerce9. relativity10. priority11. continuity / con tinual12. actuality1. In (actuality) , it was the poor peasants and blue-collar workers who complained louder about andsuffered more from the curre nt tax policy.2. The purchase in sura nee covers (mecha ni cal) breakdow n for one year, which is stated in the in sura nce policy form.3. The salespers on's emoti onal state will in flue nce the customer, and the customer's buying decisions are first emotional and then are justified with (logic) .4. I don't appreciate his reply as it was in part a(n) (denial) of the criticism and in part an attempt to cha nge the issue.5. (Occasi on al) gun shots can still be heard in the district though no one seemsto know who fires the guns and if anyone is hit.6. The boss was undecided as to what to do since his decisions can have severe and (fatal) con seque nces to all the employees and the compa ny.7. Mike is well over 40 nowand is much worried about how to maintain (continuity) betwee n his youthful past and his middle-aged prese nt.8. All notions about the well-known theory of (relativity) seemto have been coming from Einstein's general theory of relativity.9. Social fund officers are expected to give high (priority) to requests for loans for the repairs in public places like schools.10. With the in crease of (commerce) in the 21st cen tury, in vestme nt in money rather than in land has become the most convenient and popular form.11. The in sura nce fee charged by the compa ny is directly (proport ion al) to the compe nsati on its clie nts try to claim from their cases.12. As con structi on progresses, workers check (horiz on tal) and vertical levels to en sure that both walls are exactly up to the desig n requireme nts.Ban ked ClozeIt's obvious that wome n have come a long way as successful professi on als. Wome n in the workplace are (1) (flourishi ng) as an in creased nu mber of wome nhave made their presence felt in many industries and professions. The sector of the female workforce has (2) (expa nded) with more and more stre ngth and thus has its (3) (ge nuine) importa nce in the professi onal world.Whether they like it or not, men have to accept that women are marching up the man ageme nt ladder con fide ntly and (4) (diplomatically). Womenused to be much more"quiet and passive" due to the relatively small nu mber of female employees in (5)(comparison) to males. Womertoday, on the other hand, have begun seeking their (6)(adm ini strative) positi ons by using all their powers of in tellige nce.Men are hierarchical and (7) (jealous) of the "beauty power" that allows wome n to get certa in things based on their physical assets. Even though there is a(n) (8) (dispute) whether many professi onal females got into positi ons of power by using their appeara nce to their adva ntage, the (9) (valid) fact is the majority of wome nhave worked hard to achieve their desired success.Wome n were con sidered as (10) (bysta nders) in the workplace for many years and it was believed that the only jobs that they could han dle were those of teachers or secretaries, but today's womencan not only hold their own positions in the workplace, but they also have the dual task of rais ing their families.Language Focus - Expressions in Use1. I surely know it's a good opport unity for us to in vest in this hous ing project,but it all (comes down to) money in the end; that is, how much money we can affordto in vest.2. Many people (take excepti on to) this report because it may imply that wome n gen erally have a weaker character and are less resp on sible for their behavior.3. There have bee n big strikes all over the country due to the recent tax reform, but the Prime Mini ster has made it clear that he won't (make con cessi ons to) the strikers.4. What surprised me was that she stared at me for a mome nt and the n (burst in to) laughter sudde nly.5. He would n ever (feel at ease with) the Fren ch: He will n ever wear the right clothes, and he will n ever feel well on goose and red wine.6. Having expected that she would become the mistress of the household and have much more freedom after her marriage, she was now disappo in ted (on both coun ts).7. Carl (took over) the duties and resp on sibilities of his father in running amanu facturi ng factory from an early age.8. Bob was popular with local soccer fans, but his popularity also (stemmed from) the fact that he made or scored vital goals when they were needed.Tran slati on英译汉|The color and style of a wedding gown can depend on the religion and culture of the wedding participants. For example, in Western cultures brides often choose a white wedding dress, while in China the traditional wedding dress is in red. Though whitehas become the most preferred color for weddi ng gow ns across the world today, thiswas not a widespread trend before the Victorian era. White became a popular optionin 1840, when Queen Victoria wore a white gown at her wedding. The official wedding photograph was widely published, and many brides chose white to become the followers of the Queen. Many people believed that the color white symbolized virginity, though this was not the original intention. As far as the style is concerned, wedding dresseswere once typically short in the front with a Ion ger train in the back. This tendency continued until the late 1960s, when it became popular to revert to long,full-skirted desig ns.婚纱礼服的颜色和款式可取决于婚礼参与者的宗教和文化。

用QCD因子化方法研究B→PV两体弱衰变过程

第26卷增刊高能物理与核物理V o1.26，Supp. 2002年12月HIGH ENERGY PHYSICS AND NUCLEAR PHYSICS Dec.，2002 Two-Body B Decays to Pseudoscalar and Vector Mesonsin QCD Factorization ApproachYANG Mao-Zhi1 YANG Ya-Dong21 (Institute of High Energy Physics, CAS, Beijing 100039, China)2 (Department of Physics, Technion, Haifa 32000, Israel)Abstract Motivated by recent CELO measurements and the progress of the theory of B decays,B→PV(P=π, K; V= K*, ρ, ω) decay modes are studied in the framework of QCD factorization.All the measured branching ratios are well accommodated in the reasonable parameter space andpredictions for other decay modes are well below the experimental upper limits.Key words factorization, weak decay, mesonB physics is one of the most important fields nowadays because it is of great help for testing the quark flavor mixing theory of the standard model and exploring the source of CP violation. Most of the theoretical studies of B decays to pseudocalar and vector final states are based on the popular Naive Factorization approach[1]. As it was ponited out years ago in Ref. [2], the dominant contribution in B decays comes from the so-called Feynman mechanism, where the energetic quark created in the weak decay picks up the soft spectator softly and carries nearly all of the final-state meson's momentum. It is also shown that Pion form factor in QCD at intermediate engery scale is dominated by Feynman mechanism[3—5]. From this point, we can understand why the naive factorization approach have worked well for B and D decays, and the many existing predictions for B decays based on naive factorization and spectator ansatz do have taken in the dominant physics effects although there are shortcommings. However, with the many new data available from CLEO and an abundance of data to arrive within few years from the B factories BaBar and Belle, it is demanded highly to go beyond the naive factorization approach.Recently, Beneke et al., have formed an interesting QCD factorization formula for B exclusive nonleptonic decays[6,7]. The factorization formula incorporates elements of the naive factorization approach (as leading contribution) and the hard-scattering approach (as subleading corrections), which allows us to calculate systematically radiative(subleading nonfactorizable) corrections to naive factorization for B exclusive nonleptonic decays. An important product of the formula is that the strong final-state interaction phases are calculable, which arise from the2 高能物理与核物理(HEP &NP) 第26卷hard-scattering kernel and hence process dependent. The strong phases are very important for studying CP violation in B decays.The amplitude of B decays to two light mesons, say M 1 and M 2, is obtained through the hadronic matrix element <M 1(p 1) M 2(p 2)⏐O i ⏐B (p )>, here M 1 denotes the final meson that picks up the light spectator quark in the B meson, and M 2 is the another meson which is composed of the quarks produced from the weak decay point of b quark. Since the quark pair, forming M 2, is ejected from the decay point of b quark carrying the large energy of order of m b , soft gluons with the momentum of order of ΛQCD decouple from it at leading order of ΛQCD /m b in the heavy quark limit. As a consequence any interaction between the quarks of M 2 and the quarks out of M 2 is hard at leading power in the heavy quark expansion. On the other hand, the light spectator quark carries the momentum of the order of ΛQCD , and is softly transferred into M 1 unless it undergoes a hard interaction.Any soft interaction between the spectator quark and other constituents in B and M 1 can be absorbed into the transition form factor of B →M 1. The non-factorizable contribution to B →M 1 M 2 can be calculated through the diagrams in Fig.1.Fig. 1. Order αs non-factorizable contributions in B →M 1M 2 decays.The O i 's incorporated in Fig.1 are the operators in the effective Hamiltonian for B decays [8], ⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛+++⎟⎟⎠⎞⎜⎜⎝⎛++=∑∑∑∑====21103g g ccqcb 21103g g uuq ub F eff2i i i i i i *i i i i i i *O C O C O C V V O C O C O C V V G H , (1)Where()()A V A V O －－ββααu 1b u u q ⋅=, ()()A V A V O －－αββαu 2b u u q ⋅=, ()()A V A V O －－ββααc 1b c c q ⋅=, ()()A V A V O －－αββαc 2b c c q ⋅=,()()AV A V O －－ββq αα3q q b q ′′⋅=∑′,()()AV A V O －－αβq βα4q q b q ′′⋅=∑′,()()AV A V O +′′′⋅=∑ββq αα5q q b q －, ()()A V A V O +′′′⋅=∑αβq βα6q q b q －, ()()A V A V e O +′′′′⋅=∑ββq q αα7q q b q 23－, ()()A V A V e O +′′′′⋅=∑αq q b q 23βq q βα8－,增刊杨茂志等：用QCD 因子化方法研究B →PV 两体弱衰变过程 3()()A V A V e O －－ββq q αα9q q b q 23′′⋅=∑′′, ()()A V A V e O －－αβq q βα10q q b q 23′′⋅=∑′′, ()()AA a g G b R m g O µνβαβµνλσ2/d π8/b 2s =. (2)Here q=d, s and (q'ε {u, d, s, c, b}), α and β are the SU (3) color indices and , A =1,...,8 are the Gell-Mann matrices, and denotes the gluonic field strength tensor. The Wilson coefficients evaluated at µ=m AαβλAG µνb scale are[8]C 1= 1.082, C 2=−0.185, C 3= 0.014, C 4=−0.035, C 5= 0.009, C 6=−0.041,C 7=−0.002/137, C 8=0.054/137, C 9=−1.292/137, C 10=0.262/137, C g =−0.143. (3) The non-factorizable contributions to B →M 1M 2 can be calculated through the diagrams in Fig.1. The details of the calculations can be found in Ref. [9]. In the numerical calculations we use[10]τ (B +) = 1.65×10－12s, τ (B 0) = 1.56×10－12s,M B = 5.2792GeV , m b = 4.8GeV , m c = 1.4GeV , f B= 0.180GeV , f π = 0.133GeV , f K = 0.158GeV , f K * = 0.214GeV , f ρ = 0.21GeV , f ω = 0.195GeV .For the chiral enhancement factors for the pseudoscalar mesons, we takeR π ±π= R K ±, 0 = －1.2 ,which are consistent with the values used in [6, 11, 12]. We should take care for R π0. As pointedout in Ref. [7], R π0 for π0 should be －2M /(m 2b (m u + m d )) and equal to R π± due to inclusion ofisospin breaking effects correctly.For the form factors, we take the results of light-cone sum rule[13,14]F B →π(0)=0.3, F B →K (0)=1.13F B →π(0), A =0.372, A =0.470,ρB 0→*K B 0→and assume (0)=1.2(0) since we find larger (0) is preferred by experimental data.ωB 0→A ρB 0→A ωB 0→A We take the leading-twist distribution amplitude (DA) φ(x ) and the twist-3 DA φ0(x ) of light pseudoscalar and vector mesons as the asymptotic form[15]φP,V (x ) =6x (1－x ), (x ) =1. (4) 0P φFor the B meson, the wave function is chosen as[16,17]()(),xM x x N x ⎥⎥⎦⎤⎢⎢⎣⎡=2B 22B 22B B 2exp 1ωφ－－ (5)with ωB =0.4GeV , and N B is the normalization constant to make(x ) =1. φ∫1Bd φx B (x ) is stronglypeaked around x =0.1, which is consistent with the observation of Heavy Quark Effective Theory that the wave function should be peaked around ΛQCD /M B .We have used the unitarity of the CKM matrix V *uq V ub +V *V cq cb +V *tq V tb =0 to decompose the4 高能物理与核物理(HEP &NP)第26卷amplitudes into terms containing , V *uq V ub and V *V cq cb , and⏐V us ⏐=λ=0.2196, ⏐V ub /V cb ⏐=0.085±0.02, ⏐V cb ⏐=0.0395±0.0017, ⏐V ud ⏐=1－λ2/2 . (6) We leave the CKM angle γ as a free parameter.The numerical results of the branching ratios B →PV are shown in Fig.2 as the function of CKM angle γ. We can see from Fig. 2(a), (b) and (c) that for the three detected channels the predicted branching ratios agree well with the CLEO experiment data [18]. Our predictions for other decay modes are well below their 90% C.L. upper limits.There are several works available with detailed analysis of the CLEO new data of the decays of B to charmless PV states[11,12,19]. It is worth to note that the shortcomings in the “generalizedfactorization” are resolved in the framework of QCD Factorization. Nonfactorizable effects are calculated in a rigorous way here instead of being parameterized by effective color number. Since the hard scattering kernals are convoluted with the light cone DAs of the mesons, gluon virtualityk 2=2b m x in the penguin diagram Fig. 1(e) has well defined meaning and leaves no ambiguity as tothe value of k 2, which has usually been treated as a free phenomenological parameter in the estimations of the strong phase generated though the BSS mechanism [20]. So that CP asymmetries are predicted soundly in this approach. We present the numerical result of the branching ratios of B →PV decays in Table 1 with the relevant strong phases shown explicitly. It shows that the strong phases are generally mode dependent.Table 1. Strong phases in the branching ratios (in units of 10－6) for thecharmless decays modes studied by CLEO. (γ =Arg V *u b )B (B －→π－ρ0)=6.65⏐0.11e －i86.5°+e －i γ⏐2B (0B →π+ρ－)=19.79⏐0.11e i9.02°+e －i γ⏐2B (0B →π－ρ+)=13.43⏐0.03e i172°+e －i γ⏐2B (B －→π－ω)=10.59⏐0.065e i26.01°+e －i γ⏐2B (0B →π0ρ0)=0.11⏐0.21e 2.90°+e －i γ⏐2B (B －→π0ρ－)=10.81⏐0.176e i7.20°+e －i γ⏐2B (0B →π－ω)=1.49×10－3⏐1.64e i148°+e －i γ⏐2B (B －→K －ρ0)=0.55⏐0.24e －i162°+e －i γ⏐2B (B －→π－⎯K *0)=0.0012⏐56.4e －i15.7°+e －i γ⏐2B (B －→K －K *0)=0.030⏐2.86e i164°+e －i γ⏐2B (B －→π0K *－)=0.59⏐2.80e －i169°+e －i γ⏐2B (B －→K －ω)=0.80⏐0.48e －i9.23°+e －i γ⏐2B (0B →K 0ω)=0.72⏐0.81e －i 11.8°+e －i γ⏐2B (⎯B 0→K －ρ+)=0.96⏐0.63e －i7.20°+e －i γ⏐2B (0B →π0⎯K *0)=0.004⏐12.89e i67.61°+e －i γ⏐2Hou, Smith and W ürthwein have performed a model dependent fit using the recent CLEOdata and found γ =114degree. Using SU (3) flavor symmetry, Gronau and Rosner have analyzedthe decays of B to charmless PV final states extensively and found several processes are consistent with cos γ < 0. In this paper we find cos γ < 0 is favored by the B 2521+－－→π－ρ0 and ⎯B 0→π－ρ++π+ρ－ if their experimental center values are taken seriously. To meet its center value with cos γ < 0 , B －→π增刊杨茂志等：用QCD 因子化方法研究B →PV 两体弱衰变过程 5－ω would indicate larger form factor i.e. A (0) > A (0). In our numerical calculation, wehave taken A (0) = 0.446 which is still consistent with the LCSR results 0.372 ± 0.074ω→B 0ρ→B 0ω→B 0[13]. It isalso interesting to note that ⎯B 0→π+ρ－ is suppressed by cos γ < 0 while ⎯B 0→π－ρ+ is enchanced. The defference between Br (⎯B 0→π+ρ－) and Br (⎯B 0→π－ρ+) is much more sensitive to γ than their sum.6 高能物理与核物理(HEP &NP) 第26卷Summarywe have calculated the branching ratios and CP asymmetries of the charmless decays B →PV(P = (π, K), V= (ρ,ω, K *)) in QCD factorization approach. We have used LCSR formfactors F B →π,K (0) and A (0) as inputs. The results of Br (B *K ,0ρ－→π－ρ0) and Br (⎯B 0→π±ρ) agree with CLEO m [18]very well and favor cos γ < 0 if their experimental center values are taken seriously. To meet its experimental center value and cos γ < 0, the decay B －→π－ω will prefer larger form factor (0). For the other decay modes, the branching ratios are predicted well below their 90% C.L. upper limits given in Ref. [18].ωB 0→A References1 Bauer M, Stech B, Wirbel M. Z. Phys., 1985, C29: 637; Z. Phys., 1987, C34: 1032 Chernyak V L, Zhitnitsky L R. Nucl. Phys., 1990, B345: 1373 Isgur N, Llewelyn-Smith C H. Phys. Rev. Lett., 1984, 52: 1080; Nucl. Phys., 1989, B317: 5264 Radyushkin A V . Acta Phys., 1984, Pol. 15: 4035 Stefanis N G . hep-ph/99113756 Beneke M, Buchalla G , Neubert M. Phys. Rev. Lett., 1999, 83: 19147 Beneke M, Buchalla G , Neubert M et al. hep-ph/00061248 Buchalla G , Buras A J, Lautenbacher M E. Rev. Mod. Phys., 1996, 68: 1125 9 YANG M Z, YANG Y Y . Phys. Rev., 2000, D62: 114019 10 Particle Data Group. Eur. Phys. J., 1998, C3: 1 11 CHENG H Y , YANG K C. hep-ph/991029112 HOU W S, Smith J G , W ürthwein F W. hep-ex/9910014 13 Ball P, Braun V M. Phys. Rev., 1998, D58: 094016 14 Ball P. JHEP09, 005(1998)15Lepage G P, Brodsky S J. Phys. Lett., 1979, B87: 359; Chernyak V L, Zhitinissky A R. Phys. Rep., 1983, 112: 173; Braun V M, Filyanov I E. Z. Phys., 1990, C48: 239 16 Keum Y Y , LI H -N, Sanda A I. Phys. Lett., 2001, B504: 2; Phys. Rev., 2001, D63: 054008 17 LÜ C D, Ukai D, YANG M Z. Phys. Rev., 2001, D63: 07400918 CLEO Collaboration. CLEO CONF 99-13; CLEO Collaboration. CLNS 99/1652 and CLEO 99-19 19 Gronau M, Rosner J L. Phys. Rev., 2000, D61: 073008 20Bander M, Silverman D, Soni A. Phys. Rev. Lett., 1979, 43: 242增刊杨茂志等：用QCD因子化方法研究B→PV两体弱衰变过程7 用QCD因子化方法研究B→PV两体弱衰变过程杨茂志1 杨亚东21 (中国科学院高能物理研究所北京 100039)2 (Department of Physics, Technion, Haifa 32000, Israel)摘要基于最近CLEO实验和B介子物理中理论研究的进展, 在QCD因子化方案下研究了B介子到一个赝标π, K和一个矢量介子ρ, ω的两体弱衰变过程.在合理的参数范围内, 理论计算与实验相符得很好.关键词因子化弱衰变介子。

运动 (最终版)1

Oxygen demand increases in table tennis exercise . Most of the alveolar distention(肺泡扩张） and the thorax（胸廓） is expanded to the maximum volume .These are very beneficial to improve the ability of respiratory （呼吸的） movement.
Long-term TaiJiQuan exercise is good for improving heart and lung function.For many old people,TaiJiQuan can help them strengthen bones .Moreover,it is a good way to relieve fatigue.It may be regarded as the real nemesis to sub health in this modern society.
Kobe is one of the best players in NBA.His shotting at the basket,penalty shotting and three-point shotting are perfect.He once set a record by scoring 81 points in one game.In addition to crazy scores,his organzing ability is also distinguished.
Zhang Jike is the reigning World and Olympic cham pion in singles. When he won the Olympic gold medal in singles,he became the fourth male player in the history of table tennis to achieve a career grand slam(大满贯）. Among all the Chinese National team players, he is known for having the best backhand technique（反手击球）.

医学英语新教材下册重点考试翻译

1. The human body is a masterpiece of art. The more one understands the functioning of the body, the greater appreciation one has for it. Even in disease, the body is quite remarkable in attempting to right what is wrong and compensate for it.人体是一个艺术的杰作。

更多的了解身体的功能,将更大的发挥它的价值。

即使在疾病时,身体也是非常引人注目，因为它尝试判断对修补错的。

2. Congenital birth defects, mental or physical, may be due to a developmental error resulting from a maternal infection such as rubella or German measles during pregnancy, the use of certain drugs, or t he mother’s excessive consumption of alcohol.精神或身体先天性出生缺陷,可能是由于母亲在怀孕期间感染风疹或德国麻疹等,使用某些药物或过度酗酒造成的发育错误。

3. Stress adversely affects the entire body, it reduces the ability of the immune system to counteract disease. Stress causes several diseases of the gastrointestinal system such as peptic ulcers and ulcerative colitis. It also aggravates respiratory ailments —asthma, for example —and other allergic conditions.压力对整个身体造成不利影响,它降低了免疫系统抵抗疾病的能力。

climate change

Scientists say in the ancient past, higher temperatures meant smaller mammals. They're studying how a brief, but dramatic climate change event affected body size.It's called the Paleocene-Eocene Thermal Maximum or PETM for short. It took place 56 million years ago and lasted about 175,000 years. That's a long time in human terms, but a blink of an eye in the geological record.Jonathan Bloch said a lot happened back then."We had known it was a really unique event for a while in the sense that it was a very rapid, large scale global warming event. And it marks one of the most important moments in mammalian evolution in the sense that we see the first occurrence of several modern orders of mammals, including the primates that are clearly traceable as the direct ancestors of the group that we're a part of, as well as the ancestors of horses, the ancestors of cows and hippos and cam els," he said.Danielle Byerley/APJonathan Bloch of the Florida Museum of Natural HistoryBloch is associate curator of vertebrate paleontology at the Florida Museum of Natural History at the University of Florida. He and colleagues from eight institutions were collecting fossils in the state of Wyoming's Bighorn Basin.Tiny horses"For the past 9 years, we've been slowly, slowly collecting teeth, and sometimes more than teeth, fragmentary jaws, of the first horses to come in. And what we started to find was som ething pretty surprising to us. We had known that the horses that cam e in initially with that event 56 million years ago were very small, about the size of a sm all dog. But what we didn't realize was that in fact when they came in they were a little bit larger than we had expected; and that through the climate event they became about 30 percent smaller and then became larger again," he said.Then, Bloch said, fellow researcher Ross Secord, now at the University of Nebraska, took a closer look at what are called oxygen isotopes. These were found in the teeth of the horses. The relationship between oxygen and carbon in these isotopes can provide much information. "What he showed was that exactly coincident with this body size change that we had docum ented there were shifts in the oxygen isotope that showed it was getting warmer as the horses were getting smaller. And then as the horses becam e larger again it became cooler," he said.They concluded that temperature change resulted in sm aller horses.Climate itself is changing through this interval by as much as 10 degrees [Celsius] at high latitudes and perhaps as low as 5 degrees in lower latitudes. So that's a large scale event and it starts to put us in the range of the kind of climate shift that is being predicted by climate models today say for the next 100 years.Looking to the past, not futureBut paleontologists, like Bloch, don't try to predict future climate change. They look to the past to try to understand the present."Because the Earth went through substantial climate change in the past – some of it very rapid and large scale –there's a record in the rocks for exactly how animals and plants responded. And so we can go back as paleontologists and just reap the benefits of those experiments. We document that by collecting fossils and studying them. And then we can report them to the world with regards to how we should think about the reaction of plants and animals to the potential future climate change. With regards to how much we know about future climate change, that's really a round for climate scie ntists and climate modelers," he said.Now, although the focus was on tiny horses 56 million years ago, the question still arises as to whether rising temperatures will mean sm aller people in the future? Bloch says that's possible. But there are a lot of factors involved. Right now, humans are getting bigger and that's generally due to better nutrition. Humans could also adapt to rising temperatures by spending more time in air conditioned spaces.There's evidence today that temperatures and mammal size are linked."What you're referring to is an observation that's been coined Bergm ann's rule. Andessentially what this rule says is that mammals of smaller size live in warmer environm ents and mammals of larger size live in cooler environm ents. And this has be en docum ented in many different species of mammals," said Bloch.So maybe the lesson for future humans is to eat well and stay cool.In the meantime, Bloch and his colleagues will continue to collect fossils in the Bighorn Basin. He says their future discoveries may be of interest to climate scientists.Their latest findings can be found in the February 24th issue of Science magazine.。

颈部疼痛临床实践指南修订2017年颈部疼痛伴有运动功能障碍说明书

Neck Pain With Mobility DeﬁcitsCommon symptoms• Central and/or unilateral neck pain• Limitation in neck motion that consistently reproduces symptoms• Associated (referred) shoulder girdle or upper extremity pain may be presentExpected exam ﬁndings • Limited cervical ROM• Neck pain reproduced at end ranges of active and passive motions• Restricted cervical and thoracic segmental mobility• Intersegmental mobility testing reveals characteristic restriction • Neck and referred painreproduced with provocation of the involved cervical or upper thoracic segments or cervical musculature• Deﬁcits in cervicoscapulotho-racic strength and motor control may be present in individuals with subacute or chronic neck painNeck Pain With Movement Coordination Impairments (WAD)Common symptoms• Mechanism of onset linked to trauma or whiplash• Associated (referred) shoulder girdle or upper extremity pain • Associated varied nonspeciﬁc concussive signs and symptoms • Dizziness/nausea• Headache, concentration, or memory di culties; confusion; hypersensitivity to mechanical, thermal, acoustic, odor, or light stimuli; heightened a ective distress Expected exam ﬁndings• Positive cranial cervical ﬂexion test• Positive neck ﬂexor muscle endurance test• Positive pressure algometry • Strength and endurance deﬁcits of the neck muscles• Neck pain with mid-range motion that worsens with end-range positions• Point tenderness may include myofascial trigger points• Sensorimotor impairment may include altered muscleactivation patterns, propriocep-tive deﬁcit, postural balance or control• Neck and referred painreproduced by provocation of the involved cervical segmentsNeck Pain With Headache(Cervicogenic)*Common symptoms*• Noncontinuous, unilateral neck pain and associated (referred) headache• Headache is precipitated or aggravated by neck movements or sustained positions/postures Expected exam ﬁndings • Positive cervical ﬂexion-rotation test• Headache reproduced with provocation of the involved upper cervical segments • Limited cervical ROM • Restricted upper cervical segmental mobility• Strength, endurance, andcoordination deﬁcits of the neck musclesNeck Pain With Radiating Pain(Radicular)Common symptoms• Neck pain with radiating (narrow band of lancinating) pain in the involved extremity• Upper extremity dermatomal paresthesia or numbness, and myotomal muscle weakness Expected exam ﬁndings• Neck and neck-related radiating pain reproduced or relieved with radiculopathy testing: positive test cluster includes upper-limb nerve mobility, Spurling’s test, cervical distraction, cervical ROM• May have upper extremity sensory, strength, or reﬂex deﬁcits associated with the involved nerve rootsEvaluation/Intervention Component 1: medical screeningAppropriate for physical therapy evaluation and interventionEvaluation/Intervention Component 2: classify condition through evaluation of clinical ﬁndings suggestive of musculoskeletal impairments of body functioning (ICF) and the associated tissue pathology/disease (ICD)Appropriate for physical therapy evaluation and intervention along with consultation with another health care providerNot appropriate for physical therapy evaluation and interventionConsultation with appropriate health care providerversusversusFigure continues on page 2.Neck Pain With Mobility DeﬁcitsAcute• Thoracic manipulation • Cervical mobilization or manipulation• Cervical ROM, stretching, and isometric strengthening exercise • Advice to stay active plus home cervical ROM and isometric exercise• Supervised exercise, including cervicoscapulothoracic and upper extremity stretching, strengthening, and endurance training• General ﬁtness training (stay active)Subacute• Cervical mobilization or manipulation• Thoracic manipulation • Cervicoscapulothoracic endurance exerciseChronic• Thoracic manipulation • Cervical mobilization• Combined cervicoscapulotho-racic exercise plus mobilization or manipulation• Mixed exercise for cervicoscapu-lothoracic regions—neuromus-cular exercise: coordination, proprioception, and postural training; stretching; strengthen-ing; endurance training; aerobic conditioning; and cognitive a ective elements• Supervised individualized exercises• “Stay active” lifestyle approaches• Dry needling, low-level laser, pulsed or high-power ultrasound, intermittentmechanical traction, repetitive brain stimulation, TENS, electrical muscle stimulationNeck Pain With Movement Coordination Impairments (WAD)Acute if prognosis is for a quick and early recovery• Education: advice to remain active, act as usual• Home exercise: pain-free cervical ROM and postural element• Monitor for acceptable progress • Minimize collar useSubacute if prognosis is for a prolonged recovery trajectory • Education: activation and counseling• Combined exercise: active cervical ROM and isometric low-load strengthening plus manual therapy (cervical mobilization or manipulation) plus physical agents: ice, heat, TENS• Supervised exercise: active cervical ROM or stretching, strengthening, endurance, neuromuscular exerciseincluding postural, coordination, and stabilization elements Chronic• Education: prognosis,encouragement, reassurance, pain management• Cervical mobilization plus individualized progressiveexercise: low-load cervicoscapu-lothoracic strengthening,endurance, ﬂexibility, functional training using cognitivebehavioral therapy principles, vestibular rehabilitation, eye-head-neck coordination, and neuromuscular coordination elements • TENSNeck Pain With Headache(Cervicogenic)Acute• Exercise: C1-2 self-SNAG Subacute• Cervical manipulation and mobilization• Exercise: C1-2 self-SNAG Chronic• Cervical manipulation • Cervical and thoracic manipulation• Exercise for cervical and scapulothoracic region:strengthening and endurance exercise with neuromuscular training, including motor control and biofeedback elements • Combined manual therapy (mobilization or manipulation) plus exercise (stretching, strengthening, and endurance training elements)Neck Pain With Radiating Pain(Radicular)Acute• Exercise: mobilizing and stabilizing elements • Low-level laser• Possible short-term collar use Chronic• Combined exercise: stretching and strengthening elements plus manual therapy for cervical and thoracic region: mobilization or manipulation• Education counseling to encourage participation in occupational and exercise activity• Intermittent tractionEvaluation/Intervention Component 3: determination of condition stage (acute/subacute/chronic)Evaluation/Intervention Component 4: intervention strategies for patients with neck painAcute, subacute, and chronic stages are time-based stages helpful in classifying patient conditions. Time-based stages are helpful in making treatment decisions only in the sense that in the acute phase, the condition is usually highly irritable (pain experienced at rest or with initial to mid-range spinal movements: before tissue resistance); in the subacute phase, the condition often exhibits moderate irritability (painexperienced with mid-range motions that worsen with end-range spinal movements: with tissue resistance); and chronic conditions often have a low degree of irritability (pain that worsens with sustained end-range spinal movements or positions: overpressure into tissue resistance). There are cases where the alignment of irritability and the duration of symptoms does not match accordingly, requiring clinicians to make judgments when applying time-based research results on a patient-by-patient basistion to neck pain. Overall, classification is critical for match-ing the intervention strategy that is most likely to provide the optimal outcome for a patient’s condition. However, it is important for clinicians to understand that patients with neck pain often exhibit signs and symptoms that fit more than 1 classification, and that the most relevant impairments of body function and the associated intervention strategies often change during the patient’s episode of care. Thus, con-tinual re-evaluation of the patient’s response to treatment and the patient’s emerging clinical findings is important for providing the optimal interventions throughout the patient’s episode of care.Component 3111For research purposes, acute, subacute, and chronic stages are time-based stages helpful in classifying patient condi-tions and in making treatment decisions. In part, they de-fine the stage of healing: in the acute phase, the condition is usually more irritable; in the subacute phase, the condition often exhibits moderate irritability; chronic conditions often have a lower degree of irritability. There are cases where the alignment of irritability and the duration of symptoms does not match, requiring clinicians to make judgments when ap-plying time-based research results on a patient-by-patient basis. Irritability is a term used by rehabilitation practitio-ners to reflect the tissue’s ability to handle physical stress,142 and is presumably related to physical status and the extent of inflammatory activity that is present. Assessment of tissue irritability relies on clinical judgment, and is important for guiding the clinical decisions regarding treatment frequency, intensity, duration, and type, with the goal of matching the optimal dosage of treatment to the status of the tissue being treated. There are other biopsychosocial elements that may relate to staging of the condition, including, but not limited to, the level of disability reported by the patient, extent of in-terrupted sleep, medication dosage, and activity avoidance.34Component 4Interventions are listed by category of neck pain, and ordered by stage (acute/subacute/chronic). Because irritability level often reflects the tissue’s ability to accept physical stress, clini-cians should match the most appropriate intervention strate-gies to the irritability level of the patient’s condition.34,45,110,111 Additionally, clinicians should attend to influences from psy-chosocial 86 and altered pain processing elements 151 in patients with conditions in all stages of recovery.Component 1111Medical screening incorporates the findings of the history and physical examination to determine whether the patient’s symptoms originate from a condition that requires referral to another health care provider. The 2012 IFOMPT International Framework for Examination of the Cervical Region, the CCR, and the NEXUS criteria, all discussed earlier, are examples of tools that may be helpful in this decision-making process. In addition to these conditions, clinicians should screen for the presence of psychosocial issues that may affect prognostica-tion and treatment decision making for rehabilitation. For ex-ample, elevated scores on the Impact of Events Scale have been associated with other severe symptoms and a longer recovery in individuals with neck pain after whiplash injury.195 Accord-ingly, identifying cognitive behavioral tendencies during the patient’s evaluation can direct the therapist to employ specific patient education strategies to optimize patient outcomes to physical therapy interventions and potentially provide indica-tions for referring the patient for consultation with another medical or mental health practitioner.8Component 2111Differential evaluation of musculoskeletal clinical findings is used to determine the most relevant physical impairments associated with the patient’s reported activity limitations and medical diagnosis. Clusters of these clinical findings, which commonly coexist in patients, are described as impairment patterns in the physical therapy literature 4 and for neck pain are classified according to the key impairment(s) of body function, along with the characteristic and distribution of pain associated with that classification. The ICD-10 and pri-mary and secondary ICF codes associated with neck pain are provided in the 2008 ICF-based neck pain CPG.29 These clas-sifications are useful in determining interventions focused on normalizing the key impairments of body function, which in turn strive to improve the movement and function of the patient and lessen or alleviate pain and/or activity limita-tions. Key clinical findings to differentiate the classifications are shown in the FIGURE . In addition, when it comes to neck-related headaches, clinicians are encouraged to refer to the International Classification of Headache Disorders 83 for a more inclusive list of headache types/classifications (https:///how-to-use-the-classification/), and to The National Institute for Health and Care Excellence 149 for ad-ditional signs, symptoms, and conditions that should be considered in patients who present with a headache in addi-Blanpied PR, Gross AR, Elliott JM, et al. Neck pain: revision 2017: clinical practice guidelines linked to the International Classifica-tion of Functioning, Disability, and Health from the Orthopaedic Section of the American Physical Therapy Association. J Orthop Sports Phys Ther . 2017;47:A1–A83. https:///10.2519/。

微扰QCD方法计算B介子三体衰变

2019年4期创新前沿科技创新与应用Technology Innovation and Application微扰QCD 方法计算B 介子三体衰变梁泽锐（西南大学物理科学与技术学院，重庆400700）粒子物理学的标准模型理论自建立起来已经成功地将强相互作用、弱相互作用和电磁相互作用统一起来。

2012年，Higgs 粒子的发现又进一步验证了标准模型的成功，至此标准模型中所预言的粒子已经全部在实验上发现。

其中，对B 物理的深入研究也是标准模型中很重要的一个分支。

近几十年来，对B 介子各种衰变过程的理论分析已经有一套相对成熟的方法-“低能有效哈密顿方法”，但是由于QCD （量子色动力学）的夸克禁闭作用，我们目前还没有完全自洽的方法从QCD 的第一原理去计算衰变过程中涉及到的强子矩阵元等物理可观测量。

基于这套“低能有效哈密顿方法”，发展起来了不少对B 介子两体非轻衰变的处理方法，其中一种就是基于QCD 动力学建立的一些微扰和非微扰的方法。

微扰QCD 因子化（PQCD ）是其中一种因子化方法。

目前，微扰QCD 因子化方法已经广泛地应用于B 介子两体和三体非轻衰变的理论计算。

微扰QCD 因子化方法的主要思想是基于k T 因子化方案，在强子矩阵元的计算中考虑价夸克中的横向动量，引入Sudakov 因子这样就能压低端点部分的行为，避免端点发散问题。

pQCD 因子化方法与QCD 因子化方法和软贡献有效理论等方法相比，优点是运动学过程中假设衰变过程是以硬胶子交换为主，这样就可以将衰变过程中硬的部分和软的部分区别开来。

硬过程是无红外发散的可微扰计算的部分，这个过程主要是计算硬散射核矩阵元，而软的过程由于是非微扰的，所以不能做微扰计算，这一部分的贡献就作为输入参数已经吸收到相应的普适波函数中。

而现在我们用到的波函数主要是从实验上抽取或者是通过相应的非微扰方法如光锥QCD 求和规则和Lattice QCD 计算得到的。

其中波函数中涉及到的非微扰参数和分布振幅也大多来源于QCD 求和规则。

DETERMINATION OF jV ub j

CITATION: K. Hagiwara
et al.
(Particle Data Group), Phys. Rev. D 66, 010001 (2002) (URL: ) June 19, 2002 st be provided. The measurements to date have made use of detector hermeticity and the well-determined beam parameters to de ne a missing momentum that is de ned as the neutrino momentum. Signal-to-background ratios (S/B) of order one have been obtained in these channels. To extract jVub j from an exclusive channel, the form factors for that channel must be known. The form factor normalization dominates the uncertainty on jVubj. The q2 dependence of the form factors, which is needed to determine the experimental e ciency, also contributes to the uncertainty, but at a much reduced level. For example, the requirement of a sti lepton for background reduction in these analyses introduces a q2 dependence to the e ciency. In the limit of a massless charged lepton (a reasonable limit for the electron and muon decay channels), the B ! ` decay depends on one form factor f1(q2 ): 2 d?(B0 ! ?`+ ) = jV j2 G2 p3 MB sin2 jf (q2)j2; (1) F ` 1 ub dy d cos ` 32 3 2 where y = q2=MB , and ` is the angle between the charged lepton direction in the virtual W (` + ) rest frame and the direction of the virtual W . For the vector meson nal states and !, three form factors, A1 , A2 and V , are necessary (see e.g., Ref. 6). Calculation of these form factors constitutes a considerable theoretical industry, with a variety of techniques now being employed. Form factors based on lattice calculations 11{23], and on light cone sum rules 24{32], currently have uncertainties in the 15% to 20% range. A variety of quark model calculations exist 33{47]. Finally, a number of other approaches 48{53], such as dispersive bounds and experimentally-constrained models based on Heavy Quark Symmetry, seek to improve the q2 range over which the form factors can be estimated without introduction of a signi cant model dependence. Unfortunately, all these calculations currently have contributions to the uncertainty that remain uncontrolled. The light cone sum rules calculations assume quark-hadron duality, o ering a \canonical" contribution to the uncertainty of 10%, but with no known means of rigorously limiting that uncertainty. The lattice calculations to date remain in the \quenched" approximation (no

新概念第四册课文翻译及学习笔记【Lesson19、20、21】

【导语】新概念英语作为⼀套世界闻名的英语教程，以其全新的教学理念，有趣的课⽂内容和全⾯的技能训练，深受⼴⼤英语学习者的欢迎和喜爱。

为了⽅便同学们的学习，为⼤家整理了⾯的新概念第四册课⽂翻译及学习笔记，希望为⼤家的新概念英语学习提供帮助!Lesson19 【课⽂】 First listen and then answer the following question. 听录⾳，然后回答以下问题。

What is going on when a person experiences rapid eye-movements during sleep? It is fairly clear that the sleeping period must have some function, and because there is so much of it the function would seem to be important. Speculations about its nature have been going on for literally thousands of years, and one odd finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest. 'Rest', in terms of muscle relaxation and so on, can be achieved by a brief period lying, or even sitting down. The body's tissues are self-repairing and self-restoring to a degree, and function best when more or less continuously active. In fact a basic amount of movement occurs during sleep which is specifically concerned with preventing muscle inactivity. If it is not a question of resting the body, then perhaps it is the brain that needs resting? This might be a plausible hypothesis were it not for two factors. First the electroencephalograph (which is simply a device for recording the electrical activity of the brain by attaching electrodes to the scalp) shows that while there is a change in the pattern of activity during sleep, there is no evidence that the total amount of activity is any less. The second factor is more interesting and more fundamental. Some years ago an American psychiatrist named William Dement published experiments dealing with the recording of eye-movements during sleep. He showed that the average individual's sleep cycle is punctuated with peculiar bursts of eye-movements, some drifting and slow, others jerky and rapid. People woken during these periods of eye-movements generally reported that they had been dreaming. When woken at other times they reported no dreams. If one group of people were disturbed from their eye-movement sleep for several nights on end, and another group were disturbed for an equal period of time but when they were no exhibiting eye-movements, the first group began to show some personality disorders while the others seemed more or less unaffected. The implications of all this were that it was not the disturbance of sleep that mattered, but the disturbance of dreaming. CHRISHER EVANS The stuff of dreams from The Listener 【New words and expressions ⽣词和短语】 speculation n. 推测 literally adv. 确实 odd adj. 奇特的 tissue n. 组织 plausible adj. 似乎有理的 hypothesis n. 假说 electroencephalograph n. 脑电图仪 electrode n. 电极 scalp n. 头⽪ psychiatrist n. 精神病学家 punctuate v. 不时介⼊ jerky adj. 急动的 disorder n. 失调 implication n. 含意，暗⽰【课⽂注释】 1.not simply a matter of...不仅仅是……。

《新概念英语第四册》第一章至第十九章精讲

《新概念英语第四册》第一章至第十九章精讲目录1. Lesson 1 --- Finding fossil man 发现化石人2. Lesson 2 --- Spare that spider不要伤害蜘蛛3. Lesson 3 --- Matterhorn man马特霍恩山区人4. Lesson 4 --- Seeing hands能看见东西的手5. Lesson 5 --- Youth青年6. Lesson 6 --- The sporting spiri 体育的精神7. Lesson 7 --- Bats蝙蝠8. Lesson 8 --- Trading standards贸易标准9. Lesson 9 --- Royal espionage 王室谍报活动10.Lesson 10 --- Silicon valley 硅谷11.Lesson 11 --- How to grow old 如何安度晚年12.Lesson 12 --- Banks and their customers银行和顾客13.Lesson 13 --- The search for oil 探寻石油14.Lesson 14 --- The Butterfly Effect 蝴蝶效应15.Lesson 15 --- Secrecy in industry 工业中的秘密16.Lesson 16 --- The modern city 现代城市17.Lesson 17 --- A man-made disease 人为的疾病18.Lesson 18 --- Porpoises 海豚19.Lesson 19 --- The stuff of dreams 话说梦的本质Lesson 1Finding fossil man 发现化石人Why are legends handed down by storytellers useful?We can read of things that happened 5,000 years ago in the Near East, where people first learned to write. But there are some parts of the world where even now people cannot write. The only way that they can preserve their history is to recount it as sagas -- legends handed down from one generation of storytellers to another. These legends are useful because they can tell us something about migrations of people who lived long ago, but none could write down what they did. Anthropologists wondered where the remote ancestors of the Polynesian peoples now living in the Pacific Islands came from. The sagas of these people explain that some of them came from Indonesia about 2,000 years ago. But the first people who were like ourselves lived so long ago that even their sagas, if they had any, are forgotten. So archaeologists have neither history nor legends to help them to find out where the first 'modern men' came from.Fortunately, however, ancient men made tools of stone, especially flint, because this is easier to shape than other kinds. They may also have used wood and skins, but these have rotted away. Stone does not decay, and so the tools of long ago have remained when even the bones of the men who made them have disappeared without trace.New words and expressions 生词与短语fossil man (title)adj. 化石人Recountv. 叙述Sagan. 英雄故事Legendn. 传说，传奇Migrationn. 迁移，移居Anthropologistn. 人类学家Archaeologistn. 考古学家Ancestorn. 祖先Polynesianadj.波利尼西亚(中太平洋之一群岛)的Indonesian. 印度尼西亚Flintn. 燧石Rotn. 烂掉本文参考译文我们从书籍中可读到5,000 年前近东发生的事情，那里的人最早学会了写字。

浙江省杭州市示范名校2025届高考英语全真模拟密押卷含解析

浙江省杭州市示范名校2025届高考英语全真模拟密押卷考生须知：1．全卷分选择题和非选择题两部分，全部在答题纸上作答。

选择题必须用2B铅笔填涂；非选择题的答案必须用黑色字迹的钢笔或答字笔写在“答题纸”相应位置上。

2．请用黑色字迹的钢笔或答字笔在“答题纸”上先填写姓名和准考证号。

3．保持卡面清洁，不要折叠，不要弄破、弄皱，在草稿纸、试题卷上答题无效。

第一部分（共20小题，每小题1.5分，满分30分）1．Some women a good salary in a job instead of staying home，but they decided not to work for the sake of the family．A．must make B．should have made C．would make D．could have made2．With no one them，the two thieves stole into the house．A．watch B．watching C．watches D．watched3．---The pr ices of vegetables are going up madly. It’s really too much for us.---But for the situation where many vegetable producing areas _____ constant low temperature, things would not be like this.A．meet with B．have met withC．met with D．had met with4．—Congratulations！I hear you’ve won the first prize in the singing competition．—You _____ be mistaken．I’m in the dance class．A．must B．may C．should D．could5．________Wuhu with Shanghai, to be frank, and you'll find it's more convenient to live in the former.A．To compare B．ComparingC．Compare D．Compared6．— How do you think I can make up with Jack?— Set aside _______ you disagree and try to find _______ you have in common.A．what; what B．what; where C．where; what D．where; whether7．We’d better go now, ______ we’ll miss the train.A．but B．so C．otherwise D．therefore8．Competed in 1891, in ________ was known as The Gilded Age, the five-story mansion is now owned by a famous actor who decides to stage a special production of Shakespeare's Hamlet.A．that B．what C．which D．it9．The possibility that Frank was lying ______ through my mind.A．swallowed B．masked C．flashed10．Father made a promise______________ I did well in the entrance exam, he would take me to Hong Kong in the summer vacation.A．if that B．ifC．that if D．that11．Sorry I’m so late, but you cannot imagine ________ great trouble I took to find your house.A．which B．howC．what D．that12．Experience is a hard teacher because she ________ the test first, the lesson afterwards.A．gives B．has given C．was giving D．would give13．She seems to prefer American TV Shows to talking to me．A．to watch B．to be watching C．watching D．having watched14．— Will it take me long to get to the Sunshine Hotel?—No, it ______ take you long. It’s not the rush hour now.A．shouldn’t B．shan’tC．mustn’t D．needn’t15．I am wondering how it ________ that you did so much work within such a short time.A．held up B．came aboutC．gave away D．called for16．My cousin insisted that she ______ to Australia for further study. But the company refused her application. A．sends B．will be sentC．be sent D．would be sent17．This car is important to our family. We would repair it at our expense _______ it break down within the first year. A．could B．wouldC．might D．should18．Molly finally agreed, _____ reluctantly, to go and see a doctor.A．afterwards B．almostC．otherwise D．somewhat19．At college, Barack Obama didn’t know that he the first black president of the United States of America. A．was to become B．becomesC．is to become D．became20．The government placed _____ on the numbers of foreign cars that could be imported.A．limitations B．administrationC．requirements D．restrictions第二部分阅读理解（满分40分）阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。

Eternal Art——Appreciation of Sailing to Byzantium

2492018年35期总第423期ENGLISH ON CAMPUSEternal Art——Appreciation of Sailing to Byzantium文/熊方瑜Byzantium is an ancient city founded by Greeks. In 330,Constantine I rebuilt the city, named it Constantinople and made it his capital. In the fifth and sixth centuries, it was notonly the capital of Eastern Roman Empire, but also the center of highly developed and characteristic art and architecture. From Yeats’ perspective, “Byzantium was the center of European civilization and the source of its spiritual philosophy, so I symbolize the search for spiritual life by a journey to that city.”Sailing to Byzantium is an old man’s sighing: naturalworld is momentary and miserable while artistic life is eternaland fabulous. The old man wants to divorce his soul fromflesh to pursue eternity afterlife. Byzantium is his destination. In the first stanza, Yeats describes the natural world, where the young of all species—birds, fish, people—are busy loving, producing and “commending” the flesh. Though, theselivings are dying from the moment of their birth, they do not notice it. “Caught in that sensual music” of life, they neglect the monuments of unaging intellect—works of art, religion or philosophy, the products of man’s non-physical imagination.In the second stanza, Yeats presents the old man’spredicament. He is like a scarecrow, concentrating on improving his soul by spiritual music. It contrasts to the “sensual music” of nature in the first stanza. And in this stanza, the old man decides to sail to “holy city of Byzantium.”The old man finally makes it to Byzantium in the thirdstanza, and the poem’s passionate climax is introduced. He vents his grievances that his heart “sick with desire” and “fastened to a dying animal.” He addresses the “sages” in Byzantium and begs them to “come from the holy fire” and spiral down to where he is. He wants them to “consumeaway” his heart, gather him into the “artifice of eternity”, and teach him how to immortalize the mortal being.And then Yeats imagines what immortality would be like. It is the haven of art, where the artist himself becomes the artifact. He becomes a golden bird, singing soul’s music to the mythical “lords and ladies of Byzantium.” In his songs, there are “what is past, or passing, or to come”. This lineechoes with the first stanza’s “What is begotten, born, and dies.” Travelling from life to death, the old man eventually comes to a state to appreciate eternal art. He recalls his life experience and recomposes them into a poem, which will be memorized by futurity.In this poem, young people are indulged in the love of“flesh” and wouldn’t walk into this paradise. While old people are too decrepit to bear the pleasure because of theiraging body and dispirited spirits. Only when people get out ofthe control of “flesh” restriction will they “perne in a gyre” in the sky of arts.Yeats, as a giant of Late Symbolism, tactfully uses manysymbols to present the spiritual world. The “samon-falls” and “mackerel-crowded seas” are the symbolizations of the secular world. Those vivid images contribute to the pictorial description of young livings’ enthusiastic but injudiciouscondition. “God”, “sages” and “holy fire” are full of religious implications, symbolizing eternal life and art. This poem combines perceptual and rational symbolizations, creating a mysterious but philosophical atmosphere.In addition to that, the comparison between the dynamicyoung man and the infirm old man succeeds in establishing two totally different views towards natural life and spiritual life. Young people are cheering for colorful material life while old man’s material life is lifeless. However, young people’sspiritual world is empty and transient while old man’s love for eternal art was passionate and eternal.The contrast between the young and the old leads to that between the ephemeral and eternal: Life is ephemeral while art is eternal. People should come to reason from the secularentertainment, and learn to respect and appreciate the art.参考文献：[1]黄宗英.英美诗歌名篇选读[M].高等教育出版社,2007.[2]顾子欣.英诗300首[M].国际文化出版公司,1996.[3]查良铮.英国现代诗选[M].湖南人民出版社,1985.【作者简介】熊方瑜(1997.4-)，女，重庆綦江人，汉族，北京师范大学外国语言文学学院英语专业在读本科生。

高考英语热点素材延深拓展(原创)：Medichine：From Leeches to Lasers(含改编高考题型)

2020届高考英语备考素材从2019年的高考试卷来看，各科的试题命制越来越凸显以核心素养为导向的命题原则。

英语高考题更是体现了鲜明的学科核心素养（语言能力、思维品质、文化意识、学习能力）。

从近三年的全国卷英语高考题型来看，说明文和应用文考查频率极高。

下文是一篇说明文，文章主要讲述了不同国家在不同时期的药物发展史。

下面将根据文章的内容并结合当前社会热点进行不同题型的命制，同时通过题型的命制和创新来预测2020年英语高考题和提高考生的备考能力、应变能力以及学习能力。

Medicine: From Leeches to LasersWhat do lasers, leeches, tree bark, and old bread have in common? They are all things that people use to make medicine or to help sick people feel better. Throughout history, people have searched for ways to live healthier and better lives. As early as 8000B.C. , people were experimenting with methods of helping sick people. Today, we have very modern technology, yet we continue to look for ways to improve medicine and our system of health care.The history of medicine extends back thousands of years. We know that, from the earliest times, people used plants as medicine. Scientists have also found evidence that people experimented with surgery 10,000 years ago.People haven’t always gone to doctors to get medical help. In Egypt around 3000B.C. , people went to their priests when they felt sick. That was because many Egyptians believed that the gods made people sick when they were angry with them. Common remedies in Egypt at this time included garlic and onions to prevent epidemics and moldy bread to heal wounds. Around this time, however, people in Egypt were also learning more about sanitation. Archaeologists there have found ruins of elaborate bathrooms and sewerage system.In Greece in 410B.C. , a man named Hippocrates concluded that people became sick for natural reasons, not because the gods were angry. He also believed that there was a connection between diet and health. During his time, doctors prescribed massage, special diets, and baths as medical treatments for their patients.In China and other Asian countries, doctors developed acupuncture as a method of treating sickness and pain. Acupuncture uses needles to help the human body fight pain and disease. Doctors have used this method for thousands of years, and many still use it today.During the Middle Ages(400-1500A.D.), a few medical schools and hospitals opened in Europe. At this time, however, doctors considered themselves to be primarily observers of patients. For them, surgery was a menial task, something a barber should do. One common medical treatment during the Middle Ages was the use of leeches to remove “bad blood” from people. Doctors thought this “bloodletting”was good for many illnesses. Unfortunately, many plagues spread through Europe at that time. Doctors could not cure these diseases, and one quarter of the population of Europe died. It didn’t help that, in the Middle Ages, many people believed that bathing could be fatal. It wasn’t uncommon for people to bathe just once a year!After the innovation of the printing press in the mid-fifteenth century, books on health and medicine became available. Leonardo da Vinci’s drawings of the human body, including all the muscles, helped doctors tremendously. Understanding the human body helped doctors treatsicknesses and make people feel better.In the nineteenth and twentieth centuries, many remarkable discoveries were made in medicine. These discoveries saved the lives of millions of people around the world. For example, in 1895, a German doctor named Roentgen developed the X-ray medicine. In 1928, the English scientist Sir Alexander Fleming discovered penicillin, the first antibiotic. Fleming discovered penicillin growing in mold on an old piece of bread!Great advances in the technology of medicine continue to be made. Today, doctors can save people’s lives by giving them a new heart or a new kidney. Hospitals now have large computers and medicines that help doctors diagnose medical problems.Although modern medicine is making many new treatments possible, doctors are learning that some of the old ways are useful too. For example, doctors are now paying more attention to the connection between diet and health. Even the leech has found a place in modern medicine. In certain kinds of surgery, up-to-data surgeons are using leeches to prevent a patient’s arteries from getting plugged up.Some people believe that nature has all of the cures for human problems. Others believe that technology is more helpful. It just might be that, together, tradition and technology will help people everywhere live better and healthier lives.名词解释:laser: a device that produces a powerful, highly controlled, narrow beam of light激光仪leech: a type of worm that sucks or takes in , blood 水蛭，蚂蟥priest: a person, usually a man, who has been trained to perform religious duties in the Christian Church, especially the Roman Catholic Church, or a person with particular duties in some other religions 牧师，神职人员epidemic: the appearance of a particular disease in a large number of people at the same time 流行病，传染archaeologist: someone who studies the buildings, graves, tools, and other objects of people who lived in the past 考古学家Hippocrates: an ancient Greek scientist who studied and taught medicine 希波克拉底（More examples about Hippocrates:①In 360 BC, Hippocrates , the father of medicine, wrote about scurvy.②From two to three thousand years ago, fatal malaria was described in Homer's Iliad, and then in the writings of Plato, Aristotle and Hippocrates.③In ancient Greece, Hippocrates recorded tuberculosis as the most widespread diseaseand almost always fatal.④Hippocrates called olive oil the "great therapeutic".）the Middle Ages: a period in European history, between about AD 1000 and AD 1500, when the powerof kings, people of high rank, and the Christian Church was strong 中世纪“bad blood”: ①feelings of hate between people because of arguments in the past 仇恨②坏血病，败血症Leonardo da Vinci: 列奥纳多达芬奇——欧洲文艺复兴时期的天才科学家、发明家、画家。

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September, 1998
Charmless Hadronic Two-body Decays of Bs Mesons
Yaw-Hwang Chen,a Hai-Yang Cheng,b B. Tsengb
a
Department of Physics, National Cheng-Kung University Tainan, Taiwan 700, Republic of China
b
arXiv:hep-ph/9809364v2 1 Dec 1998
Institute of Physics, Academia Sinica Taipei, Taiwan 115, Republic of China
Abstract
Two-body charmless nonleptonic decays of the Bs meson are studied within the framework of generalized factorization in which factorization is applied to the tree level matrix elements while the eﬀective Wilson coeﬃcients are µ and renormalization scheme independent, and nonfactorizeﬀ (LL) and N eﬀ (LR), the eﬀective numbers of colors able eﬀects are parametrized in terms of Nc c arising from (V − A)(V − A) and (V − A)(V + A) four-quark operators, respectively. Branching ratios of Bs → P P, P V, V V decays (P : pseudoscalar meson, V : vector meson) are calculated as a eﬀ (LR) with two diﬀerent considerations for N eﬀ (LL): (a) N eﬀ (LL) being ﬁxed at function of Nc c c eﬀ (LL) = N eﬀ (LR). Tree and penguin transitions are classiﬁed into six the value of 2, and (b) Nc c diﬀerent classes. We ﬁnd that (i) the electroweak penguin contributions account for about 85% eﬀ (LL) = 2) of the decay rates of B → ηπ, η ′ π, ηρ, η ′ ρ, φπ, φρ, which receive contribu(for Nc s tions only from tree and electroweak penguin diagrams; a measurement of them will provide a clean determination of the electroweak penguin coeﬃcient a9 , (ii) electroweak penguin corrections ′ to Bs → ωη ( ) , φη, ωφ, K (∗) φ, φφ are in general as signiﬁcant as QCD penguin eﬀects and even eﬀ (LR), (iii) the branching ratio of play a dominant role; their decay rates depend strongly on Nc Bs → ηη ′ , the analogue of Bd → η ′ K , is of order 2 × 10−5 , which is only slightly larger than that 0 of η ′ η ′ , K ∗+ ρ− , K + K − , K 0 K decay modes, (iv) the contribution from the η ′ charm content is important for Bs → η ′ η ′ , but less signiﬁcant for Bs → ηη ′ , and (v) the decay rates for the ﬁnal states ∗+ ∗− K +(∗) K −(∗) follow the pattern: Γ(B s → K + K − ) > Γ(B s → K + K ∗− ) > ∼ Γ(B s → K K ) > Γ(B s → K +∗ K − ) and likewise for K 0(∗) K , as a consequence of various interference eﬀects between the penguin amplitudes governed by the eﬀective QCD penguin coeﬃcients a4 and a6 .
0(∗)
1
I. INTRODUCTION
Recently there has been a remarkable progress in the study of exclusive charmless B decays, both experimentally and theoretically. On the experimental side, CLEO has discovered many new two-body decay modes [1]:
0 0 B → η ′ K + , η ′ KS , π ± KS , π ± K ∓ , π 0 K ± , ωK ± ,
(1.1)
and a possible evidence for B → φK ∗ . Moreover, CLEO has improved upper limits for many other channels. Therefore, it is a ﬁeld whose time has ﬁnally arrived. On the theoretical aspect, many important issues have been studied in past years, such as the eﬀective Wilson coeﬃcients that are renormalization scale and scheme independent, nonfactorizable eﬀects in hadronic matrix elements, the QCD anomaly eﬀect in the matrix element of pseudoscalar densities, running light quark masses at the scale mb , and the q 2 dependence of form factors. In the present paper, we plan to extend previous studies of charmless hadronic decays of − B , Bd mesons to the Bs mesons. In principle, the physics for the Bs two-body hadronic decays is very similar to that for the Bd meson except that the spectator d quark is replaced by the s quark. Experimentally, it is known that B ± → η ′ K ± and Bd → η ′ K have abnormally large branching ratios, several times larger than previous predictions. It would be very interesting to see if the analogue of Bd → η ′ K , namely Bs → ηη ′ or Bs → η ′ η ′ still has the largest branching ratio in two-body Bs charmless decays. Another point of interest is concerned with the electroweak penguin corrections. It is naively believed that in charmless B decays, the contributions from the electroweak penguin diagrams are negligible compared to the QCD penguin corrections because of smallness of electroweak penguin Wilson coeﬃcients. As pointed out in [2], some Bs decay modes receive contributions only from the tree and electroweak penguin diagrams and moreover they are dominated by the latter. Therefore, electroweak penguins do play a dominant role in some of Bs decays. There also exist several penguin-dominated Bs decay modes in which electroweak penguin corrections to the decay rate are comparable to that of QCD penguin contributions. In this paper, we will study this in details. Experimentally, only upper limits on the branching ratios have been established for a few Bs rare decay modes (see [3] or Table 7 of [1]) and most of them are far beyond the theoretical expectations. Nevertheless, it is conceivable that many of the Bs charmless decays can be seen at the future hadron colliders with large b production. Theoretically, early systematical studies can be found in [4,5]. More recently, one of us (B.T.) [6] has analyzed the exclusive charmless Bs decays involving the η or η ′ within the framework of generalized factorization. This paper is organized as follows. A calculational framework is set up in Sec. II in which we discuss the cale and scheme independent Wilson coeﬃcient functions, parametrization of nonfactorizable eﬀects, classiﬁcation of factorizable amplitudes,..., etc. The numerical results and discussions are presented in Sec. III. Conclusions are summarized in Sec. IV. The factorizable amplitudes for all the charmless two-body Bs decays are given in Appendices.