Perturbative predictions for B_c meson production in hadronic collisions

a rXiv:h ep-ph/9212266v116Dec1992SLAC–PUB–6017WIS–92/99/Dec–PH December 1992T/E The Subleading Isgur-Wise Form Factor χ3(v ·v ′)to Order αs in QCD Sum Rules Matthias Neubert Stanford Linear Accelerator Center Stanford University,Stanford,California 94309Zoltan Ligeti and Yosef Nir Weizmann Institute of Science Physics Department,Rehovot 76100,Israel We calculate the contributions arising at order αs in the QCD sum rule for the spin-symmetry violating universal function χ3(v ·v ′),which appears at order 1/m Q in the heavy quark expansion of meson form factors.In particular,we derive the two-loop perturbative contribution to the sum rule.Over the kinematic range accessible in B →D (∗)ℓνdecays,we find that χ3(v ·v ′)does not exceed the level of ∼1%,indicating that power corrections induced by the chromo-magnetic operator in the heavy quark expansion are small.(submitted to Physical Review D)I.INTRODUCTIONIn the heavy quark effective theory(HQET),the hadronic matrix elements describing the semileptonic decays M(v)→M′(v′)ℓν,where M and M′are pseudoscalar or vector mesons containing a heavy quark,can be systematically expanded in inverse powers of the heavy quark masses[1–5].The coefficients in this expansion are m Q-independent,universal functions of the kinematic variable y=v·v′.These so-called Isgur-Wise form factors characterize the properties of the cloud of light quarks and gluons surrounding the heavy quarks,which act as static color sources.At leading order,a single functionξ(y)suffices to parameterize all matrix elements[6].This is expressed in the compact trace formula[5,7] M′(v′)|J(0)|M(v) =−ξ(y)tr{(2)m M P+ −γ5;pseudoscalar meson/ǫ;vector mesonis a spin wave function that describes correctly the transformation properties(under boosts and heavy quark spin rotations)of the meson states in the effective theory.P+=1g s2m Q O mag,O mag=M′(v′)ΓP+iσαβM(v) .(4)The mass parameter¯Λsets the canonical scale for power corrections in HQET.In the m Q→∞limit,it measures thefinite mass difference between a heavy meson and the heavy quark that it contains[11].By factoring out this parameter,χαβ(v,v′)becomes dimensionless.The most general decomposition of this form factor involves two real,scalar functionsχ2(y)andχ3(y)defined by[10]χαβ(v,v′)=(v′αγβ−v′βγα)χ2(y)−2iσαβχ3(y).(5)Irrespective of the structure of the current J ,the form factor χ3(y )appears always in the following combination with ξ(y ):ξ(y )+2Z ¯Λ d M m Q ′ χ3(y ),(6)where d P =3for a pseudoscalar and d V =−1for a vector meson.It thus effectively renormalizes the leading Isgur-Wise function,preserving its normalization at y =1since χ3(1)=0according to Luke’s theorem [10].Eq.(6)shows that knowledge of χ3(y )is needed if one wants to relate processes which are connected by the spin symmetry,such as B →D ℓνand B →D ∗ℓν.Being hadronic form factors,the universal functions in HQET can only be investigated using nonperturbative methods.QCD sum rules have become very popular for this purpose.They have been reformulated in the context of the effective theory and have been applied to the study of meson decay constants and the Isgur-Wise functions both in leading and next-to-leading order in the 1/m Q expansion [12–21].In particular,it has been shown that very simple predictions for the spin-symmetry violating form factors are obtained when terms of order αs are neglected,namely [17]χ2(y )=0,χ3(y )∝ ¯q g s σαβG αβq [1−ξ(y )].(7)In this approach χ3(y )is proportional to the mixed quark-gluon condensate,and it was estimated that χ3(y )∼1%for large recoil (y ∼1.5).In a recent work we have refined the prediction for χ2(y )by including contributions of order αs in the sum rule analysis [20].We found that these are as important as the contribution of the mixed condensate in (7).It is,therefore,worthwhile to include such effects also in the analysis of χ3(y ).This is the purpose of this article.II.DERIV ATION OF THE SUM RULEThe QCD sum rule analysis of the functions χ2(y )and χ3(y )is very similar.We shall,therefore,only briefly sketch the general procedure and refer for details to Refs.[17,20].Our starting point is the correlatord x d x ′d ze i (k ′·x ′−k ·x ) 0|T[¯q ΓM ′P ′+ΓP +iσαβP +ΓM+Ξ3(ω,ω′,y )tr 2σαβ2(1+/v ′),and we omit the velocity labels in h and h ′for simplicity.The heavy-light currents interpolate pseudoscalar or vector mesons,depending on the choice ΓM =−γ5or ΓM =γµ−v µ,respectively.The external momenta k and k ′in (8)are the “residual”off-shell momenta of the heavy quarks.Due to the phase redefinition of the effective heavy quark fields in HQET,they are related to the total momenta P and P ′by k =P −m Q v and k ′=P ′−m Q ′v ′[3].The coefficient functions Ξi are analytic in ω=2v ·k and ω′=2v ′·k ′,with discontinuities for positive values of these variables.They can be saturated by intermediate states which couple to the heavy-light currents.In particular,there is a double-pole contribution from the ground-state mesons M and M ′.To leading order in the 1/m Q expansion the pole position is at ω=ω′=2¯Λ.In the case of Ξ2,the residue of the pole is proportional to the universal function χ2(y ).For Ξ3the situation is more complicated,however,since insertions of the chromo-magnetic operator not only renormalize the leading Isgur-Wise function,but also the coupling of the heavy mesons to the interpolating heavy-light currents (i.e.,the meson decay constants)and the physical meson masses,which define the position of the pole.1The correct expression for the pole contribution to Ξ3is [17]Ξpole 3(ω,ω′,y )=F 2(ω−2¯Λ+iǫ) .(9)Here F is the analog of the meson decay constant in the effective theory (F ∼f M√m QδΛ2+... , 0|j (0)|M (v ) =iF2G 2tr 2σαβΓP +σαβM (v ) ,where the ellipses represent spin-symmetry conserving or higher order power corrections,and j =¯q Γh (v ).In terms of the vector–pseudoscalar mass splitting,the parameter δΛ2isgiven by m 2V −m 2P =−8¯ΛδΛ2.For not too small,negative values of ωand ω′,the coefficient function Ξ3can be approx-imated as a perturbative series in αs ,supplemented by the leading power corrections in 1/ωand 1/ω′,which are proportional to vacuum expectation values of local quark-gluon opera-tors,the so-called condensates [22].This is how nonperturbative corrections are incorporated in this approach.The idea of QCD sum rules is to match this theoretical representation of Ξ3to the phenomenological pole contribution given in (9).To this end,one first writes the theoretical expression in terms of a double dispersion integral,Ξth 3(ω,ω′,y )= d νd ν′ρth 3(ν,ν′,y )1Thereare no such additional terms for Ξ2because of the peculiar trace structure associated with this coefficient function.possible subtraction terms.Because of theflavor symmetry it is natural to set the Borel parameters associated withωandω′equal:τ=τ′=2T.One then introduces new variables ω±=12T ξ(y) F2e−2¯Λ/T=ω0dω+e−ω+/T ρth3(ω+,y)≡K(T,ω0,y).(12)The effective spectral density ρth3arises after integration of the double spectral density over ω−.Note that for each contribution to it the dependence onω+is known on dimensionalgrounds.It thus suffices to calculate directly the Borel transform of the individual con-tributions toΞth3,corresponding to the limitω0→∞in(12).Theω0-dependence can be recovered at the end of the calculation.When terms of orderαs are neglected,contributions to the sum rule forΞ3can only be proportional to condensates involving the gluonfield,since there is no way to contract the gluon contained in O mag.The leading power correction of this type is represented by the diagram shown in Fig.1(d).It is proportional to the mixed quark-gluon condensate and,as shown in Ref.[17],leads to(7).Here we are interested in the additional contributions arising at orderαs.They are shown in Fig.1(a)-(c).Besides a two-loop perturbative contribution, one encounters further nonperturbative corrections proportional to the quark and the gluon condensate.Let usfirst present the result for the nonperturbative power corrections.WefindK cond(T,ω0,y)=αs ¯q q TT + αs GG y+1− ¯q g sσαβGαβq√y2−1),δn(x)=1(4π)D×1dλλ1−D∞λd u1∞1/λd u2(u1u2−1)D/2−2where C F=(N2c−1)/2N c,and D is the dimension of space-time.For D=4,the integrand diverges asλ→0.To regulate the integral,we assume D<2and use a triple integration by parts inλto obtain an expression which can be analytically continued to the vicinity of D=4.Next we set D=4+2ǫ,expand inǫ,write the result as an integral overω+,and introduce back the continuum threshold.This givesK pert(T,ω0,y)=−αsy+1 2ω0dω+ω3+e−ω+/T(16)× 12−23∂µ+3αs9π¯Λ,(17)which shows that divergences arise at orderαs.At this order,the renormalization of the sum rule is thus accomplished by a renormalization of the“bare”parameter G2in(12).In the9π¯Λ 1µ2 +O(g3s).(18)Hence a counterterm proportional to¯Λξ(y)has to be added to the bracket on the left-hand side of the sum rule(12).To evaluate its effect on the right-hand side,we note that in D dimensions[17]¯Λξ(y)F2e−2¯Λ/T=3y+1 2ω0dω+ω3+e−ω+/T(19)× 1+ǫ γE−ln4π+2lnω+−ln y+12T ξ(y) F2e−2¯Λ/T=αsy+1 2ω0dω+ω3+e−ω+/T 2lnµ6+ y r(y)−1+ln y+1According to Luke’stheorem,theuniversalfunction χ3(y )vanishes at zero recoil [10].Evaluating (20)for y =1,we thus obtain a sum rule for G 2(µ)and δΛ2.It reads G 2(µ)−¯ΛδΛ224π3ω00d ω+ω3+e −ω+/T ln µ12 +K cond (T,ω0,1),(21)where we have used that r (1)=1.Precisely this sum rule has been derived previously,starting from a two-current correlator,in Ref.[16].This provides a nontrivial check of our ing the fact that ξ(y )=[2/(y +1)]2+O (g s )according to (19),we find that the µ-dependent terms cancel out when we eliminate G 2(µ)and δΛ2from the sum rule for χ3(y ).Before we present our final result,there is one more effect which has to be taken into account,namely a spin-symmetry violating correction to the continuum threshold ω0.Since the chromo-magnetic interaction changes the masses of the ground-state mesons [cf.(10)],it also changes the masses of higher resonance states.Expanding the physical threshold asωphys =ω0 1+d M8π3 22 δ3 ω032π2ω30e −ω0/T 26π2−r (y )−ξ(y ) δ0 ω096π 248T 1−ξ(y ).It explicitly exhibits the fact that χ3(1)=0.III.NUMERICAL ANALYSISLet us now turn to the evaluation of the sum rule (23).For the QCD parameters we take the standard values¯q q =−(0.23GeV)3,αs GG =0.04GeV4,¯q g sσαβGαβq =m20 ¯q q ,m20=0.8GeV2.(24) Furthermore,we useδω2=−0.1GeV from above,andαs/π=0.1corresponding to the scale µ=2¯Λ≃1GeV,which is appropriate for evaluating radiative corrections in the effective theory[15].The sensitivity of our results to changes in these parameters will be discussed below.The dependence of the left-hand side of(23)on¯Λand F can be eliminated by using a QCD sum rule for these parameters,too.It reads[16]¯ΛF2e−2¯Λ/T=9T4T − ¯q g sσαβGαβq4π2 2T − ¯q q +(2y+1)4T2.(26) Combining(23),(25)and(26),we obtainχ3(y)as a function ofω0and T.These parameters can be determined from the analysis of a QCD sum rule for the correlator of two heavy-light currents in the effective theory[16,18].Onefinds good stability forω0=2.0±0.3GeV,and the consistency of the theoretical calculation requires that the Borel parameter be in the range0.6<T<1.0GeV.It supports the self-consistency of the approach that,as shown in Fig.2,wefind stability of the sum rule(23)in the same region of parameter space.Note that it is in fact theδω2-term that stabilizes the sum rule.Without it there were no plateau.Over the kinematic range accessible in semileptonic B→D(∗)ℓνdecays,we show in Fig.3(a)the range of predictions forχ3(y)obtained for1.7<ω0<2.3GeV and0.7<T< 1.2GeV.From this we estimate a relative uncertainty of∼±25%,which is mainly due to the uncertainty in the continuum threshold.It is apparent that the form factor is small,not exceeding the level of1%.2Finally,we show in Fig.3(b)the contributions of the individual terms in the sum rule (23).Due to the large negative contribution proportional to the quark condensate,the terms of orderαs,which we have calculated in this paper,cancel each other to a large extent.As a consequence,ourfinal result forχ3(y)is not very different from that obtained neglecting these terms[17].This is,however,an accident.For instance,the order-αs corrections would enhance the sum rule prediction by a factor of two if the ¯q q -term had the opposite sign. From thisfigure one can also deduce how changes in the values of the vacuum condensates would affect the numerical results.As long as one stays within the standard limits,the sensitivity to such changes is in fact rather small.For instance,working with the larger value ¯q q =−(0.26GeV)3,or varying m20between0.6and1.0GeV2,changesχ3(y)by no more than±0.15%.In conclusion,we have presented the complete order-αs QCD sum rule analysis of the subleading Isgur-Wise functionχ3(y),including in particular the two-loop perturbative con-tribution.Wefind that over the kinematic region accessible in semileptonic B decays this form factor is small,typically of the order of1%.When combined with our previous analysis [20],which predicted similarly small values for the universal functionχ2(y),these results strongly indicate that power corrections in the heavy quark expansion which are induced by the chromo-magnetic interaction between the gluonfield and the heavy quark spin are small.ACKNOWLEDGMENTSIt is a pleasure to thank Michael Peskin for helpful discussions.M.N.gratefully acknowl-edgesfinancial support from the BASF Aktiengesellschaft and from the German National Scholarship Foundation.Y.N.is an incumbent of the Ruth E.Recu Career Development chair,and is supported in part by the Israel Commission for Basic Research and by the Minerva Foundation.This work was also supported by the Department of Energy,contract DE-AC03-76SF00515.REFERENCES[1]E.Eichten and B.Hill,Phys.Lett.B234,511(1990);243,427(1990).[2]B.Grinstein,Nucl.Phys.B339,253(1990).[3]H.Georgi,Phys.Lett.B240,447(1990).[4]T.Mannel,W.Roberts and Z.Ryzak,Nucl.Phys.B368,204(1992).[5]A.F.Falk,H.Georgi,B.Grinstein,and M.B.Wise,Nucl.Phys.B343,1(1990).[6]N.Isgur and M.B.Wise,Phys.Lett.B232,113(1989);237,527(1990).[7]J.D.Bjorken,Proceedings of the18th SLAC Summer Institute on Particle Physics,pp.167,Stanford,California,July1990,edited by J.F.Hawthorne(SLAC,Stanford,1991).[8]M.B.Voloshin and M.A.Shifman,Yad.Fiz.45,463(1987)[Sov.J.Nucl.Phys.45,292(1987)];47,801(1988)[47,511(1988)].[9]A.F.Falk,B.Grinstein,and M.E.Luke,Nucl.Phys.B357,185(1991).[10]M.E.Luke,Phys.Lett.B252,447(1990).[11]A.F.Falk,M.Neubert,and M.E.Luke,SLAC preprint SLAC–PUB–5771(1992),toappear in Nucl.Phys.B.[12]M.Neubert,V.Rieckert,B.Stech,and Q.P.Xu,in Heavy Flavours,edited by A.J.Buras and M.Lindner,Advanced Series on Directions in High Energy Physics(World Scientific,Singapore,1992).[13]A.V.Radyushkin,Phys.Lett.B271,218(1991).[14]D.J.Broadhurst and A.G.Grozin,Phys.Lett.B274,421(1992).[15]M.Neubert,Phys.Rev.D45,2451(1992).[16]M.Neubert,Phys.Rev.D46,1076(1992).[17]M.Neubert,Phys.Rev.D46,3914(1992).[18]E.Bagan,P.Ball,V.M.Braun,and H.G.Dosch,Phys.Lett.B278,457(1992);E.Bagan,P.Ball,and P.Gosdzinsky,Heidelberg preprint HD–THEP–92–40(1992).[19]B.Blok and M.Shifman,Santa Barbara preprint NSF–ITP–92–100(1992).[20]M.Neubert,Z.Ligeti,and Y.Nir,SLAC preprint SLAC–PUB–5915(1992).[21]M.Neubert,SLAC preprint SLAC–PUB–5992(1992).[22]M.A.Shifman,A.I.Vainshtein,and V.I.Zakharov,Nucl.Phys.B147,385(1979);B147,448(1979).FIGURESFIG.1.Diagrams contributing to the sum rule for the universal form factorχ3(v·v′):two-loop perturbative contribution(a),and nonperturbative contributions proportional to the quark con-densate(b),the gluon condensate(c),and the mixed condensate(d).Heavy quark propagators are drawn as double lines.The square represents the chromo-magnetic operator.FIG.2.Analysis of the stability region for the sum rule(23):The form factorχ3(y)is shown for y=1.5as a function of the Borel parameter.From top to bottom,the solid curves refer toω0=1.7,2.0,and2.3GeV.The dashes lines are obtained by neglecting the contribution proportional toδω2.FIG.3.(a)Prediction for the form factorχ3(v·v′)in the stability region1.7<ω0<2.3 GeV and0.7<T<1.2GeV.(b)Individual contributions toχ3(v·v′)for T=0.8GeV and ω0=2.0GeV:total(solid),mixed condensate(dashed-dotted),gluon condensate(wide dots), quark condensate(dashes).The perturbative contribution and theδω2-term are indistinguishable in thisfigure and are both represented by the narrow dots.11。

2025高考英语步步高大一轮复习讲义人教版必修第一册高考题型组合练必修第一册Unit 4Natural DisastersⅠ.阅读理解A(★)As a shift in the polar vortex(极地涡旋) swept across much of the US，many people in the country were hit with a sudden snap of cold.Heavy ice and snow coupled with fallen trees caused the outages in major cities，with companies unable to tell their customers when power will be restored.Polar vortices were noticed long ago.But the first known use of the term “polar vortex” was in a magazine in 1853.Polar vortices are present year-round，but we don’t hear about them until they cause problems.They maintain freezing temperatures at the North and South Poles by moving in tight counterclockwise patterns.Polar vortices grow stronger in winter and weaken in summer.They are kept in place at the poles by another atmospheric current called the jet stream.However，when the jet streams weaken，the cold winds of the polar vortex are pushed southwards and it is during this time that people begin to pay attention!In Texas，roads froze over，causing six traffic deaths，and many schools were shut down.People are not the only Earthlings to struggle with the cold.Crops and animals are also freezing.This could have major consequences，especially if herds of cattle die.If snow blocks cattle，the animals can’t reach basic necessities like food and fresh water.On a brighter note，some Texas cities were more prepared than others，for instance，Amarillo，which is located in North Texas，so they are more accustomed to colder temperatures.Amarillo is notable because the city was redesigned to stand up to severe winter storms.Officials have spread out fire stations to increase coverage of first responders，employed modified dump trucks for clearing ice，and upgraded civic centers to provide shelter during storms.Hopefully，other Texas cities will follow the good example set by Amarillo!1．What does the underlined word “outages” refer to in paragraph 1?A．Traffic jams. B．Power struggles. C．Power cuts. D．Traffic accidents.2．What can we learn about polar vortices?A．They grow stronger in summer. B．They are affected by jet streams.C．They were first observed in 1853. D．They move in a clockwise direction.3．What is the last but one paragraph mainly about?A．The definition of the polar vortex.B．The characteristics of the polar vortex.C．The ways to deal with the polar vortex.D．The serious impact made by the polar vortex.4．Why is Amarillo striking?A．Because it is located in the north of Texas.B．Because it has been upgraded and modernized.C．Because it has been regarded as an example to other cities.D．Because it has taken effective measures to resist winter storms.BWhat is the 15-minute city？It’s the urban planning concept that everything city residents need should be a short walk or bike ride away—about 15 minutes from home to work，shopping，entertainment，restaurants，schools，parks and health care.Supporters argue that 15-minute cities are healthier for residents and the environment，creating united mini-communities，boosting local businesses，and encouraging people to get outside walk，and cycle.Many cities across Europe offer similar ideas，but Paris has become its poster child.Mayor Anne Hidalgo has sought to fight climate change by decreasing choking traffic in the streets and fuel emissions.In 2015，Paris was 17th on the list of bike-friendly cities; by 2019，it was 8th.Car ownership，meanwhile，dropped from 60 percent of households in 2001 to 35 percent in 2019.The 15-minute city figured largely in Hidalgo’s successful 2020 re-election campaign.The idea has also gained support in the U．S.It clearly won’t work everywhere：Not every city is as centralized and walkable as Paris.Some car-dominated cities like Los Angeles and Phoenix would be hard-pressed to provide everything people need within walking distance.In addition，some urban planners argue that the 15-minute city could increase the separation of neighborhoods by income.Neighborhoods equipped with all the conveniences required by the 15-minute city also tend to have high housing costs and wealthier residents.Despite some resistance，the basic principles behind the 15-minute city are influencing planning in cities around the world，including Melbourne，Barcelona，Buenos Aires，Singapore，and Shanghai.Urban designer and thinker Jay Pitter says cities where basic needs are within walking distance create more individual freedom than needing to drive everywhere.“In a city where services are always close by，” he says，“mobility is a choice：You go where you want because you want to，not because you have to.My fight is not against the car.My fight is how we could improve the quality of life.”5．Which best describes the 15-minute city?A．Modern. B．Smart. C．Entertaining. D．Convenient.6．What’s the original intention for Paris to advocate the 15-minute city?A．To address climate issues. B．To beautify the city.C．To promote the bike industry. D．To help Hidalgo get re-elected.7．What’s some urban planners’ worry about the 15-minute city?A．It slows the city’s expansion.B．It represents a setback for society.C．It may widen the gap between neighborhoods.D．It can cause the specialization of neighborhoods.8.What’s Jay Pitter’s attitude to the concept of 15-minute city?A．Doubtful. B．Favorable. C．Critical. D．Uninterested.C(★)Earthquake forecasting is one of the most ancient skills known to mankind.From ancient Greece to the present day，countless scientists have tried to develop tools to predict earthquakes.Their attempts usually focused on searching for reliable evidence of coming quakes.However，there are many reasons why predicting quakes is so hard.“We don’t understand some basic physics of earthquakes，” said Egill，a research professor at the California Institute of Technology.Scientists have also attempted to create mathematical models of movement，but precisely predicting would require great mapping and analysis of the Earth’s crust.Other challenges include a lack of data on the early warning signs，given that these warning signs are not yet entirely understood.Actually，real earthquake prediction is very similar to the diagnosis of potential human illnesses based on observing and analyzing each patient’s signs and symptoms.As it turns out，quake prediction is extremely difficult.Many sources show that earthquake forecasting was recognized science in ancient Greece.Ancient Greeks lived very close to nature and were able to detect unusual phenomena and forecast earthquakes.The first known forecast was made by Pherecydes of Syros about 2,500 years ago：he made it as he scooped water from a well and noticed that usually very clean water had suddenly become muddy.Indeed，an earthquake occurred two days later，making Pherecydes famous.Nowadays，seismic(地震的) and remote-sensing methods are considered to have the greatest potential in terms of solving the earthquake prediction problem.Currently，Terra Seismic can identify a forthcoming earthquake with a high level of confidence.Generally，Terra Seismic does not predict a quake if the earthquake’s epicenter is located beyond a depth of 40km.Fortunately，such quakes are almost always harmless，since quake’s energy reduces before reaching the Earth’s surface.“Scientists have tried every possible method to try to predict earthquakes，” Bruneau said.“Nobody has been able to crack it and make a believable prediction.”9．What do we know about earthquake forecasting?A．Scientists have been passionate about accurately predicting earthquakes.B．As long as enough data is collected，earthquakes can be avoided.C．Mathematical models of motion can simulate and predict earthquakes.D．Scientists have fully studied the structure of earthquakes.10．How did Pherecydes successfully predict that earthquake?A．By seismic and remote-sensing methods.B．By observing unusual natural phenomena.C．By living in seismic zones throughout the year.D．By looking into data on the early warning signs.11．What was Bruneau’s opinion about the current methods of earthquake prediction? A．He strongly believed the Terra Seismic can solve the difficult problem.B．He was sure that humans could accurately predict earthquakes in the future.C．He considered it harmless to humans for an earthquake deeper than 40km.D．He thought that scientists had no reliable method to predict earthquakes.12．What is the text mainly about?A．Why do humans predict earthquakes.B．How to protect oneself during an earthquake.C．What methods can be used to forecast earthquakes.D．When to achieve accurate earthquake forecasting.Ⅱ.七选五(★)Hurricane season can be wild and unpredictable. 1 Here are some ways you can beef up your home security in hurricane weather，even if you need to move out.2 That actually does nothing to ensure your safety in the powerful winds.Sticking to hurricane shelters or plywood(胶合板) is the only way to go when it comes to protecting those points of entry in hurricane conditions.Buy sheets of plywood，measure your windows and use brackets(支架) to hold the plywood in place.Sandbags are very useful.While sandbags won’t be able to help in the extreme storm，many people will be able to prevent flooding and extensive damage to their belongings by placing sandbags. 3 Any storm water that is kept out of your home is storm water that won’t be able to damage the belongings inside your home，so sandbags are well worth having at your doorways during a hurricane.It’s important to prepare the inside of your home for strong winds and rain.But you should also keep an eye on the outside of your house，too.Trim(修剪) trees，especially dead branches，to prevent anything else that could fly through a window and cause damage during a hurricane. 4 You should also take pictures of expensive items like electronics and keep notes of their serialnumbers. 5 Also，there are always bad people out right after a storm.If the worst happens and your home is broken into right after a bad storm，having pictures and detailed notes about what was in your home prior to the hurricane will make it easier for police to track down stolen items. A．You should have a camera at home.B．It can be strong enough to resist the forceful winds.C．Making sure nothing is loose in your yard is important.D．You may see people taping windows before a hurricane comes.E．They will be able to effectively keep storm water out in many cases.F．It will aid with your insurance company if anything needs to be replaced.G．These dangerous storms can bring damage to your home and belongings.必修第一册Unit 5Languages Around the WorldⅠ.阅读理解AMost of us take the task of buying a cup of coffee for granted，as it seems simple enough.However，we have no idea just how stressful tasks like this can be for people who suffer from disabilities.That’s why it’s so heart-warming to see a story like this in which a barista (咖啡师) does something small to make life a little easier for someone who is deaf.Ibby Piracha lost his hearing when he was only two years old，and he now goes to his local cafe in Leesburg，Virginia to order a cup of coffee at least three times a week.Though all the baristas who work there have his order memorized，Ibby always writes his order on his phone and shows it to the barista.One day，however，one of the baristas did something that changed everything! After Ibby ordered his coffee，he was amazed when barista Krystal Pane handed him a note in response.“I’ve been learning sign language just so you can have the same experience as everyone else，” the note read.Krystal then asked Ibby in sign language what he would like to order.Ibby was touched that she would learn sign language just to help him feel welcome.“I was just so moved that she actually wanted to learn sign language.It is really a totally different language and it was something that she wanted to do because of me.Because I was a deaf customer.I was very，very impressed，” Ibby said.Krystal had spent hours watching teaching videos so that she could learn enough sign language to give Ibby the best customer service that she could! “My job is to make sure peoplehave the experience they expect and that’s what I gave him，” Krystal says.Ibby posted a photo of Krystal’s note online，and it quickly went viral，getting hundreds of likes and comments that praised Krystal for her kind action.1．What can we learn about Ibby Piracha from paragraph 2?A．He was born deaf. B．He lives a hard life.C．He loves to order take-out food. D．He visits the cafe regularly.2．Why did Krystal learn sign language?A．To serve Ibby better. B．To attract more customers.C．To give Ibby a big surprise. D．To make herself more popular.3．Which of the following can best describe Krystal?A．Kind and considerate. B．Honest and responsible.C．Sociable and humorous. D．Ambitious and sensitive.4．What message does the author want to convey in the text?A．Two heads are better than one. B．A small act makes a difference.C．One good turn deserves another. D．Actions speak louder than words.B(★)(2024·湖北武汉调研)When I mentioned to some friends that we all have accents，most of them proudly replied，“Well，I speak perfect English/Chinese/etc.” But this kind of saying misses the point.More often than not，what we mean when we say someone “has an accent” is that their accent is different from the local one，or that pronunciations are different from our own.But this definition of accents is limiting and could give rise to prejudice.Funnily enough，in terms of the language study，every person speaks with an accent.It is the regular differences in how we produce sounds that define our accents.Even if you don’t hear it yourself，you speak with some sort of accent.In this sense，it’s pointless to point out that someone “has an accent”．We all do!Every person speaks a dialect，too.In the field of language study，a dialect is a version of a language that is characterized by its variations of structure，phrases and words.For instance，“You got eat or not？”(meaning “Have you eaten？”) is an acceptable and understood question in Singapore Oral English.The fact that this expression would cause a standard American English speaker to take pause doesn’t mean that Singapore Oral English is “wrong”or “ungrammatical”．The sentence is well-formed and clearly communicative，according to native Singapore English speakers’ solid system of grammar.Why should it be wrong just because it’s different?We need to move beyond a narrow conception of accents and dialects—for the benefit ofeveryone.Language differences like these provide insights into people’s cultural experiences and backgrounds.In a global age，the way one speaks is a distinct part of one’s identity.Most people would be happy to talk about the cultures behind their speech.We’d learn more about the world we live in and make friends along the way.5．What does the author think of his/her friends’ response in paragraph 1?A．It reflects their self confidence.B．It reflects their language levels.C．It misses the point of communication.D．It misses the real meaning of accents.6．Why does the author use the example of Singapore Oral English?A．To justify the use of dialects. B．To show the diversity of dialects.C．To correct a grammatical mistake. D．To highlight a traditional approach.7．What does the author recommend us to do in the last paragraph?A．Learn to speak with your local dialect.B．Seek for an official definition of accents.C．Appreciate the value of accents and dialects.D．Distinguish our local languages from others’．8．What can be a suitable title for the passage?A．Everyone Has an Accent B．Standard English Is at RiskC．Accents Enhance Our Identities D．Dialects Lead to MisunderstandingⅡ.完形填空One summer night in a seaside cottage，a small boy was in bed，sound asleep.Suddenly，he felt himself 1 from bed and carried in his father’s arms onto the beach.Overhead was the clear starry sky.“Watch！” As his father spoke， 2 ，one of the stars moved.It 3 across the sky like a golden fire.And before the 4 of this could fade，another star leapt from its place，then another...“What is it？” the child asked in 5 .“Shooting stars.They 6 every year on a certain night in August.”That was all：just an 7 encounter of something magic and beautiful.But，back in bed，the child stared into the dark，with mind full of the falling stars.I was the 8 seven-year-old boy whose father believed that a new experience 9 more for a small boy than an unbroken night’s sleep.That night，my father opened a door for his child，leading him into an area of splendid10 .Children are naturally curious，but they need someone to 11 them.This art of adding new dimensions to a child’s world doesn’t 12 require a great deal of time.It simply 13 doing things more often with children instead of for them or to them.Good parents know this：The most precious gift they can give a child is to spark their flame of 14 .That night is still deeply 15 in my memory.Next year，when August comes with its shooting stars，my son will be seven.1．A.hidden B．robbed C．lifted D．kicked2．A.incredibly B．accidentally C．apparently D．actually3．A.exploded B．circled C．spread D．flashed4．A.success B．wonder C．exhibition D．discovery5．A.amazement B．horror C．relief D．delight6．A.blow up B．turn up C．show off D．give out7．A.uncomfortable B．unbearable C．undetected D．unexpected8．A.curious B．fortunate C．determined D．chosen9．A.worked B．mattered C．deserved D．proved10．A.newness B．emptiness C．freedom D．innovation11．A.protect B．challenge C．guide D．believe12．A.absolutely B．basically C．possibly D．necessarily13．A.involves B．risks C．admits D．resists14．A.hope B．faith C．curiosity D．wisdom15.A.trapped B．set C．lost D．rootedⅢ.语法填空(★)The Olympics are a series of international athletic competitions held in different countries.They’re 1. important multi-sport event that takes place every four years.For the Olympics，participants from all over the world train for years and try their best 2. (win)．Pierre Coubertin，a French man,3. (found) the International Olympic Committee (IOC) in 1894.He was once a teacher and historian.In his honor，French had the official status(地位) and 4. (prior) over other languages at the Olympics.According to the Olympic Charter，English and French are the official languages of the Olympics.Therefore，every participant needs to have their documents 5. (translate) in both languages.Besides，real-time interpretations in Arabic，German，Russian，and Spanish must be available for all sessions.The IOC has a complete guide for those 6. want to apply to these contests.French has the status of being the first official language for Olympic events and it was the language of diplomacy (外交) in the beginning.But later，more countries considered 7. (participate) in this contest.The IOC then made French and English the official languages of the Olympics.8．(actual)，more than 100 countries in the world speak English now.Besides，almost every country has made 9. a must that children learn English in schools and colleges.This 10. (influence) status has caused the IOC to make English one of the official languages.必修第一册Welcome UnitⅠ.阅读理解AThroughout all the events in my life，one in particular sticks out more than the others.As I reflect on this significant event，a smile spreads across my face.As I think of Shanda，I feel loved and grateful.It was my twelfth year of dancing，I thought it would end up like any other year：stuck in emptiness，forgotten and without the belief of any teacher or friend that I really had the potential to achieve greatness.However，I met Shanda，a young，talented choreographer(编舞者)．She influenced me to work to the best of my ability，pushed me to keep going when I wanted to give up，encouraged me and showed me the real importance of dancing.Throughout our hard work，not only did my ability to dance grow，but my friendship with Shanda grew as well.With the end of the year came our show time.As I walked to a backstage filled with other dancers，I hoped for a good performance that would prove my improvement.I waited anxiously for my turn.Finally，after what seemed like days，the loudspeaker announced my name.Butterflies filled my stomach as I took trembling steps onto the big lighted stage.But，with the determination to succeed and eagerness to live up to Shanda’s expectations for me，I began to dance.All my troubles and nerves went away as I danced my whole heart out.As I walked up to the judge to receive my first-place shining，gold trophy(奖杯)，I realized that dance is not about becoming the best.It is about loving dance for dance itself，a getaway from all my problems in the world.Shanda showed me that you could let everything go and just dance what you feel at that moment.After all the doubts that people had in me，I believed in myself and did not care what others thought.Thanks to Shanda，dance became more than a love of mine，but a passion.1．What did the author think her dancing would be for the twelfth year?A．A change for the better. B．A disappointment as before.C．A proof of her potential. D．A pride of her teachers and friends.2．How did Shanda help the author?A．By offering her financial help. B．By entering her in a competition.C．By coaching her for longer hours. D．By awakening her passion for dancing.3．How did the author feel when she stepped on the stage?A．Proud. B．Nervous. C．Scared. D．Relieved.4．What can we learn from the author’s story?A．Success lies in patience. B．Fame is a great thirst of the young.C．A good teacher matters. D．A youth is to be treated with respect.B(★)Are you a good judge of character？Can you make an accurate judgement of someone’s personality based only on your first impression of them？Interestingly，the answer lies as much in them as it does in you.One of the first people to try to identify good judges of character was US psychologist Henry F Adams in 1927.His research led him to conclude that people fell into two groups—good judges of themselves and good judges of others.Adams’s research has been widely criticized since then，but he wasn’t entirely wrong about there being two clearly different types.More on that in a moment，but first we need to define what a good judge of character is.Is it someone who can read personality or someone who can read emotion？Those are two different skills.Emotions such as anger or joy or sadness can generate easily identifiable physical signs.Most of us would probably be able to accurately identify these signs，even in a stranger.As such，most of us are probably good judges of emotion.In order to be a good judge of personality，however，there needs to be an interaction with the other person，and that person needs to be a “good target”．“Good targets” are people who reveal relevant and useful signals to their personality.So this means “the good judge” will only manifest when reading “good targets”．This is according to Rogers and Biesanz in their 2019 journal entitled “Reassessing the good judge of personality”．“We found consistent，clear and strong evidence that the good judge does exist，” Rogers and Biesanz concluded.But their key finding is that the good judge does not have magical gifts of perception—they are simply able to “detect and use the information provided by the good target”．So，are first impressions really accurate？Well，if you’re a good judge talking to a “good target”，then it seems the answer is “yes”．And now we know that good judges probably do exist，more research can be done into how they read personality，what kind of people they are—and whether their skills can be taught.5．What can we learn about Adams from paragraph 2?A．He is a good judge of character.B．He divided psychologists into two groups.C．His research result has been widely accepted.D．His research on good judges was partially right.6．What does the author think of emotion reading?A．Annoying. B．Joyful. C．Simple. D．Strange.7.Which of the following would Rogers and Biesanz agree with?A．A good target is necessary for personality judgement.B．A good target needs to get his personality reassessed.C．A good judge can provide useful signals to our personality.D．It’s possible to be a good judge just by looking at the other person.8．What does the author think future research should focus on?A．The skills of good communication. B．The features of good judges.C．The ways to read personality. D．The accuracy of first impressions.C(2023·新课标Ⅱ，C)Reading Art: Art for Book Lo v ers is a celebration of an everyday object—the book，represented here in almost three hundred artworks from museums around the world.The image of the reader appears throughout history，in art made long before books as we now know them came into being.In artists’ representations of books and reading，we see moments of shared humanity that go beyond culture and time.In this “book of books”，artworks are selected and arranged in a way that emphasizes these connections between different eras and cultures.We see scenes of children learning to read at home or at school，with the book as a focus for relations between the generations.Adults are portrayed(描绘) alone in many settings and poses—absorbed in a volume，deep in thought or lost in a moment of leisure.These scenes may have been painted hundreds of years ago，but they record moments we can all relate to.Books themselves may be used symbolically in paintings to demonstrate the intellect(才智)，wealth or faith of the subject.Before the wide use of the printing press，books were treasured objects and could be works of art in their own right.More recently，as books have become inexpensive or even throwaway，artists have used them as the raw material for artworks—transforming covers，pages or even complete volumes into paintings and sculptures.Continued developments in communication technologies were once believed to make the printed page outdated.From a 21st-century point of view，the printed book is certainly ancient，but it remains as interactive as any battery-powered e-reader.To serve its function，a book must be activated by a user: the cover opened，the pages parted，the contents reviewed，perhaps notes written down or words underlined.And in contrast to our increasingly networked lives where theinformation we consume is monitored and tracked，a printed book still offers the chance of a wholly private，“off-line” activity.9．Where is the text most probably taken from?A．An introduction to a book. B．An essay on the art of writing.C．A guidebook to a museum. D．A review of modern paintings.10．What are the selected artworks about?A．Wealth and intellect. B．Home and school.C．Books and reading. D．Work and leisure.11．What do the underlined words “relate to” in paragraph 2 mean?A．Understand. B．Paint. C．Seize. D．Transform.12．What does the author want to say by mentioning the e-reader?A．The printed book is not totally out of date.B．Technology has changed the way we read.C．Our lives in the 21st century are networked.D．People now rarely have the patience to read.Ⅱ.七选五Wonderful views from the mountains，breathtaking places waiting to explore，fresh air，as well as all the special health benefits，are the main rewards of mountain hiking. 1You need to train your lower body muscles，anytime and anywhere.Strong legs and core muscles will improve your balance and help you hike longer.Focus on your lower body strength and on your cardiovascular(心血管的) workout. 2 You really can train anywhere：use your backyard，living room，or bedroom to keep your body ready for the true conditions in the mountains.You will need a stronger back.Who’s going to carry your backpack？ 3 So we are quite sure what the true answer is.Develop back muscles with exercises like V-ups，deadlifts，diver push-ups，and exercise named “mountain climbers”：Start in a traditional plank(平板支撑) position and then bring your knee forward under your chest.You will start to feel your abs(腹肌) for sure，too.4 Even Rome wasn’t built in a day so give yourself the pleasure to enjoy discovering what your body is capable of! All the perfect benefits will improve your blood pressure and blood sugar levels，helping you strengthen your core，and even help you control your weight as an additional benefit.5 Just don’t forget to stretch after each training.Please remember that your training for mountain hiking should be combined with real hiking.And don’t miss the other clues on what to do for mountaineering training!。

高考英语气候变化的全球影响与应对单选题30题1.Climate change refers to long-term shifts in temperature and weather patterns. What is one major cause of climate change?A.Natural disastersB.Human activitiesC.Astronomical eventsD.Animal behaviors答案：B。

本题主要考查对气候变化原因的理解。

选项A 自然灾害不是气候变化的主要原因；选项C 天文事件对气候变化影响较小；选项D 动物行为对气候变化影响微乎其微。

而人类活动，如燃烧化石燃料、砍伐森林等，是导致气候变化的主要原因之一。

2.Which of the following is a sign of climate change?A.Frequent rainstormsB.Clear skiesC.Calm windsD.Warm winters only答案：A。

气候变化的表现包括极端天气增多，频繁的暴雨是其中之一。

选项B 晴朗的天空不是气候变化的标志；选项C 平静的风也不是；选项D 仅仅是暖冬不能全面代表气候变化，气候变化有多种表现。

3.What does the term “greenhouse gases” refer to?A.Gases that cool the planetB.Gases that are only produced by natureC.Gases that trap heat in the atmosphereD.Gases that are harmless to the environment答案：C。

“greenhouse gases”指的是温室气体，能在大气中捕获热量。

选项A 温室气体是使地球升温而非降温；选项B 温室气体也有人为产生的；选项D 温室气体对环境并非无害。