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The Roper and Radiative Decay of Pentaquarks

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a r X i v :h e p -p h /0412132v 4 3 J a n 2005The Roper and Radiative Decay of PentaquarksDeog Ki Hong ∗Department of Physics,Pusan National University,Busan 609-735,Korea andCenter for Theoretical Physics,MassachusettsInstitute of Technology,Cambridge,MA 02139,USA(Dated:February 2,2008)Abstract Identifying the Roper N (1440)and N (1710)as the pentaquark octet and anti-decuplet,respec-tively,we analyze their main decay modes in the diquark picture.The ratio of the partial decay widths is largely consistent with the nearly ideal mixing of the Jaffe-Wilczek diquark model,which then allows to predict the width of the radiative decay of N (1440),Γ10(N →pγ)=1/4Γ12(N →nγ)=0.25−0.31MeV.We then show that the three-body radiative decay of the pentaquark anti-decuplet is quite enhanced due to its mixing with the pentaquark octet.We find for the J P =1∗E-mail:dkhong@pusan.ac.kr,dkhong@Since the discovery of a narrow state of exotic baryons in the photon-nucleon scattering at LEPS[1]as predicted by chiral soliton models[2],several models have been proposed for exotic baryons[3].However,in spite of the active theoretical study on exotic baryons, the current experimental situation of pentaquarks[4]is quite confusing,as some of the subsequent experiments have not seen them.In this letter,we analyze the decay modes of N(1440)and N(1710)to show that they are consistent with the Jaffe-Wilczek(JW)diquark model[5].We then point out that the three-body radiative decay of the pentaquark anti-decuplet can be quite enhanced due to the near degeneracy between the octet and the anti-decuplet and also the diquark nature of pentaquarks.Since the radiative decay amplitude is proportional to the electric charge of the anti-quark bound in the pentaquark,the diquark model predictsΓ(Θ+→K+nγ)=4Γ(Θ+→K0pγ),which will be a clear signal for the diquark models.In the JW model,the exotic baryons are bound states of two scalar diquarks and one anti-quark,forming the multiplets of low dimensions,10and8is lifted by a nearly ideal mixing between them.It was soon confirmed by NA49experiments[6],which discovered S=−2pentaquarks of mass1860MeV,not much different from the JW prediction.The decay widths of pentaquarks are also explicitly calculated in the diquark effective theory based on the JW model tofind they are naturally small,a few MeV or less,since they decay through tunnelling the potential barrier between two diquarks[7].In the JW model,the lightest member of the pentaquark octet is identified,after mixing, as the Roper state N(1440).Its orthogonal state in the anti-decuplet is identified as N(1710). Though the assignmentfits well in the mass formula,it is argued in[8,9]that such an identification leads to a gross violation of SU(3)in partial decay widths,unseen in other hadronic decays.However,we show that the partial decay widths of N(1440)and N(1710) are consistent with the JW model,because the gross violation is due to the fact that the exotic baryons decay by tunneling,whose amplitude depends exponentially on the SU(3) violating terms.Another concern[10]was that the decay branching fraction for∆(1600)→N(1440)πis not suppressed at all,Γ1/Γ=10−25%[11].But,since the exotic baryon production is suppressed not by tunneling but only by the production amplitude of diquarks, whose strength is nothing but the Yukawa coupling of the diquark to two quarks,g≈1.7[7], the observed branching ratio does not necessarily contradict with the diquark picture.Finally,we show that a three-body radiative decay is quite enhanced and contributes significantly to the decay of the pentaquark anti-decuplet.In the JW model,due to the mixing,the diquarks inside the octet are closer to each other than in the anti-decuplet,making tunnelling easier for the octet.Furthermore,since the octet and the anti-decuplet are almost degenerate,the virtual octet in the three-body decay of the anti-decuplet is near on-shell and makes the three-body decay more efficient.In the ideal mixing,the quark content of the S =0component of the pentaquark octet is N 1=|¯q ,ϕud ,ϕud ,where ¯q is the light anti-quark and ϕud is the diquark made of u andd ,while the S =0component of the pentaquark anti-decuplet is N 2=|¯s ,ϕqs ,ϕud ,where the ϕqs diquark is made of the light quark q and the strange quark,s .The dominant decay modes of N 1and N 2are shown in the diquark picture in Fig.1.From the viewpoint of the chiral perturbation theory,the processes shown in Fig.1(a)uud d p p p k k 22131N N (a)πq1s u d p p p k k 22131K N (b)Λs q 2FIG.1:The dominant decay modes of excited nucleons:(a)N 1→Nπ(b)N 2→ΛK .The breaking of diquark occurs through tunneling.and (b)should not differ by more than 30%,the typical size of SU(3)breaking terms.However,the experimental data differs by an order of magnitude,if N 1and N 2are iden-tified as N (1440)and N (1710),respectively:Γa (N (1440)→N π)=210−245MeV and Γb (N (1710)→ΛK )=5−25MeV.This may seem to contradict with the diquark picture.But,a gross difference in the decay widths of two processes is expected,since the SU(3)violating terms appear in the exponent of the tunneling amplitude in the diquark picture.The decay widths are given respectively asΓa =g 2πN N 1M 2N (1440) M N (1440)−m N 2−m 2π (1)Γb =g 2K ΛN 2M 2N (1710) M N (1710)−m Λ 2−m 2K ,(2)where the outgoing meson momenta are| k1|=396MeV and| k′1|=268MeV,respectively.From the partial widths by the Particle Data Group(PDG),we get gπN N1=±(0.3∼0.33)and g KΛN2=±(0.10∼0.23).The amplitude for exotic baryons to decay into normal baryons is quite suppressed due to the tunneling barrier for the diquarks[7].Therefore,the couplings in the decay of N1 and N2have to be proportional to their tunneling amplitudes.The WKB approximation for the tunneling amplitude for N1gives e−S0(N1)≃e−∆E r0=0.26,where the potential barrier is approximately the binding energy of quarks in the scalar diquark,∆E≃270MeV,and r0≃(201MeV)−1is the average distance between two diquarks of N1in P-wave.The distance is estimated from the mass formula for the naive diquark modelM N1=2M ud+m q+1e−S0(N2)≃1.7,gπN N12/3+δ. Then N2≃|¯s,ϕsq,ϕud +δ|¯q,ϕud,ϕud and the partial decay width becomesΓ(N(1710)→Nπ)≈δ2Γ(N(1440)→Nπ),(5)which givesδ=±|gπN N2/gπN N1|≈±0.26or the mixing angleθ≈20◦.Wefirst examine the radiative decay of the Roper N(1440).Assuming it is the mixed pentaquark N1,we have drawn the diagram for the radiative decay in Fig.2(a),neglectingγudud (k )p p p 1231N (a)N qq k 21γ(b)N N1FIG.2:The radiative decay of the Roper N(1440)the angle δ.The leading interaction for the radiative decay of the pentaquark octet in the chiral perturbation theory (Fig.2.b)is given asL (1)O Bγ=e ∗¯B A Q e O +h .c .(6)where B is the normal baryon octet,A µis the photon field,and Q e is the electric charge matrix acting on the anti-quark bound in the pentaquark octet,O .The effective electric charge e ∗is proportional to the tunneling amplitude,e −S 0(N 1),since the decay occurs by annihilation of a quark bound in a diquark after the other quark in the diquark tunnels to another diquark.For the radiative decay we get,after summing over the photon polarization,Γ(N 1→Nγ)=Q 2e e 2∗M 3N 1× 2M N 1m N −(M N 1−m N )2 =e 2∗Q 2e 156MeV ,(7)where Q e is the electric charge of the anti-quark in the pentaquark octet.Since the decay amplitude is proportional to the electric charge of the anti-quark we get at the leading order Γ(N 1→nγ)=4Γ(N 1→pγ).Comparing the decay processes N 1→Nπ(Fig.1.a)and N 1→Nγ(Fig.2.a),we obtain e ∗g A =e g πN N 1,where g A ≃0.75is the quark axial coupling in the quark ing the coupling obtained from the decay width for N (1440)→Nπ,we get e ∗=0.4−0.44e .Then,the partial radiative decay width becomes Γ(N 1→pγ)=0.25∼0.31MeV,which isabout 2times larger that the estimate made by PDG [13].Finally,we consider the three-body radiative decay of pentaquarks.The diagram for Θ+→KN and the dominant diagram [14]for Θ+→KNγin the diquark effective theory are shown in Fig.3.The same processes in the chiral perturbation theory are drawn in Fig.4.The exotic baryons in the anti-decuplet are coupled to the octet exotics by thes u u d d p p p k k 22131K (a)N K γu d u d (k )(k )13p p p 123s (b)N q q k 2FIG.3:The decay modes of Θ+:(a)two-body decay and (b)three-body radiative decay.ΘK(a)N +γΘKp k k k 123(b)NN +1FIG.4:The decay processes of Θ+in chiral perturbation theorymeson octet,as well as to the ground state baryon octet.The leading interaction terms for the decay of the pentaquark anti-decuplet and the pentaquark octet are given in the SU(3)limit asL (1)=C P B ¯P γ5a B +g PO ¯P γ5a O +D O B Tr ¯O γ5{ a ,B } +F O B Tr ¯O γ5[a ,B ] +h .c .(8)where P and O are the anti-decuplet and octet pentaquarks,respectively,and a µ=i/2(ξ†∂µξ−ξ∂µξ†)is the axial current of the meson octet,ξ=exp (iπa T a /f ).(T a ’s are the SU(3)generators.)The couplings C PB ,D O B ,F O B are proportional to the axial coupling g A ,the Yukawa coupling between the diquark and quarks,g ,and the tunneling amplitude e −S 0[7].The pentaquark octet will decay into the ground state baryon octet and other particles.But,only the radiative decay is allowed for the virtual octet in the three-body decay of the anti-decuplet pentaquarks because the allowed phase space is below the threshold of any hadronic decays for the intermediate pentaquark octet.The differential cross-section for the three-body decay Θ+→K Nγ(Fig.4.b)is givenat tree-level as dΓ(Θ+→K Nγ)128π3m 3K256π3m 4K2g A =2.12,the naive quark model value.In the SU(3)limit the Θ+coupling to the octet meson and the ground state baryon is related to the physical couplings of N (1440)and N (1710),which are mixed states of2g πN N 1sin θ−√We note that the systematic difference (of about 12MeV)in the measurement of the Θ+mass between K 0p and K +n ,noted in [17],may be due to the missing photons in the radiative decay,Θ+→K 0p γ[18].In the K 0p decay channel,the Θ+mass is reconstructed from the invariant mass,M K 0p ,of K 0and p ,while it is measured from the missing mass in the K +n decay process.But,when there is a missing photon of momentum k 3in theK 0p decay channel of Θ+,the invariant mass is given in the rest frame of Θ+as M 2K 0p =M 2Θ+−2M Θ+| k 3|.The probability of finding the photon of energy in | k 3|∼| k 3|+d | k 3|in the K 0p channel is1d | k 3| d | k 3|.(11)where Γtot =Γ(Θ+→K 0p )+Γ(Θ+→K 0pγ)and dΓ3body is the differential three-body radiative decay width in Eq.(9),after integrating over θγ.Averaging over the photon energy distribution,we getM 2K 0p =M 2Θ+−0.26M Θ+m K Γ3bodyThe three-body radiative decay is quite significant in the decay ofΘ+,especially in the forward decay,since it has a peak when the outgoing kaon and nucleon are collinear.Our analysis suggests that one should take into account the radiative decay in search of the pentaquark decay.AcknowledgmentsWe are grateful to V.D.Burkert,M.Forbes,K.Hicks,R.Jaffe,E.Lomon,V.Mohta,D. Pirjol,M.Prasza l owicz,M.Savage,I.Stewart,and F.Wilczek for useful discussions.This work is supported by Korea Research Foundation Grant(KRF-2003-041-C00073)and also in part by funds provided by the U.S.Department of Energy(D.O.E.)under cooperative research agreement#DF-FC02-94ER40818.[1]T.Nakano et al.[LEPS Collaboration],Phys.Rev.Lett.91(2003)012002[arXiv:hep-ex/0301020].[2] D.Diakonov,V.Petrov and M.V.Polyakov,Z.Phys.A359,305(1997)[arXiv:hep-ph/9703373];M.Praszalowicz,in Proceedings,“Skyrmions And Anomalies”, M.Jezabek and M.Praszalowicz,eds.,World Scientific(1987),p.112;A.V.Manohar,Nucl.Phys.B248,19(1984);M.Chemtob,Nucl.Phys.B256,600(1985).[3]For recent reviews,see R.L.Jaffe,arXiv:hep-ph/0409065;M.Karliner and H.J.Lipkin,arXiv:hep-ph/0307243;M.Praszalowicz,arXiv:hep-ph/0410241.[4]For a recent overview on the pentaquarks experiments,see G.Trilling in[11].[5]R.L.Jaffe and F.Wilczek,Phys.Rev.Lett.91(2003)232003[arXiv:hep-ph/0307341].[6] C.Alt et al.[NA49Collaboration],Phys.Rev.Lett.92,042003(2004)[arXiv:hep-ex/0310014].[7] D.K.Hong,Y.J.Sohn and I.Zahed,Phys.Lett.B596,191(2004)[arXiv:hep-ph/0403205].[8]T.D.Cohen,Phys.Rev.D70,074023(2004)[arXiv:hep-ph/0402056].[9]K.Goeke,H.C.Kim,M.Praszalowicz and G.S.Yang,arXiv:hep-ph/0411195.[10]V.Mohta,arXiv:hep-ph/0411247.[11]S.Eidelman et al.[Particle Data Group Collaboration],Phys.Lett.B592,1(2004).[12] D.K.Hong and C.j.Song,arXiv:hep-ph/0407274.[13]In a recent experiment at JLab,they found strong longitudinal response to N(1440)inγ∗+p→N(1440)[19].[14]There are other tree diagrams for the radiative decay,but they are all suppressed,since theydo not have N1or have more powers of the electric charge.[15]T.Mehen and C.Schat,Phys.Lett.B588,67(2004)[arXiv:hep-ph/0401107].[16]P.Ko,J.Lee,T.Lee and J.h.Park,arXiv:hep-ph/0312147;[17]P.Rossi[CLAS Collaboration],arXiv:hep-ex/0409057;K.Hicks,arXiv:hep-ex/0412048.[18]The author thanks K.Hicks for discussions on this.[19]I.G.Aznauryan,V. D.Burkert,H.Egiyan,K.Joo,R.Minehart and L. C.Smith,arXiv:nucl-th/0407021.。

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2024年04版小学六年级上册第14次英语第4单元真题[含答案]

2024年04版小学六年级上册第14次英语第4单元真题[含答案]

2024年04版小学六年级上册英语第4单元真题[含答案]考试时间：80分钟（总分:140）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题共100分)1. 填空题：I think it’s important to ________ (学习新事物).2. 听力题：She has a ________ for her birthday.3. 填空题：I think it’s important to ________ (关注健康).4. 听力题：A flammable substance can easily catch _______.5. 选择题：What is the opposite of sad?A. HappyB. JoyfulC. CheerfulD. All of the above答案:D6. 听力题：A saturated solution can reach its limit when no more solute can be ______.7. 填空题：I enjoy playing ________ (棋类) with my friends.8. 填空题：The hawk's talons are sharp and designed for capturing ________________ (猎物).9. 选择题：How many wheels does a bicycle have?A. 2B. 3C. 4D. 510. 听力题：A substance that conducts electricity in solution is called an ______.11. 听力题：The __________ is a large area of untouched nature.12. 选择题：What do you call the vehicle that travels on tracks?A. CarB. TrainC. PlaneD. Boat答案: B13. 听力题：Reactivity is the ability of a substance to undergo a _____.14. 填空题：The pigeon is often found in _______ (城市).15. 选择题：What is the color of a typical cantaloupe?A. OrangeB. GreenC. YellowD. Red答案:A16. 听力题：I enjoy ______ (baking) cookies with my mom.17. 填空题：The __________ (历史的动态) highlight change over time.18. 填空题：A ______ (蜥蜴) can change colors to hide from predators.19. 填空题：I can explore different cultures with my ________ (玩具).He is a _____ (评论员) on a popular podcast.21. 选择题：What is the opposite of hot?A. WarmB. ColdC. CoolD. Freezing答案:B22. 填空题：My friend has a great sense of __________ (风趣).23. 填空题：My ________ (玩具名称) is a fun way to learn about animals.24. 听力题：A light-year is a measure of ______.25. 填空题：The rain is ________ (太大了).26. 填空题：__________ (物质循环) describes how elements move through the ecosystem.27. 填空题：我的朋友喜欢 _______ (活动). 她觉得这很 _______ (形容词)28. 填空题：The _______ (老虎) is a fierce predator.29. 听力题：Iron reacts with oxygen to form _______.30. 填空题：My favorite snack is _______ and crunchy.31. 听力题：Many _______ are edible and delicious.32. 填空题：We need to _______ (保持) a healthy lifestyle.What do you wear on your hands in winter?A. SocksB. MittensC. BootsD. Hat答案：B34. 填空题：The ______ (植物的生态影响) can be studied through various means.35. 填空题：My mom enjoys __________ (锻炼) and keeping fit.36. 填空题：The sunset is _______ (美丽的).37. 填空题：Did you see the _____ (兔子) hopping around?38. 听力题：The _____ (car/bike) is red.39. 听力题：I like to _____ (swim) in the pool.40. 填空题：A __________ day is great for going to the park. (晴朗的)41. 填空题：A ____(biophilia) is an innate affinity for nature.42. 听力题：A wheel makes it easier to _______ things.43. 听力题：The chemical symbol for zinc is ______.44. 选择题：What is the capital of Spain?A. MadridB. BarcelonaC. ValenciaD. Seville答案:A45. (15) is famous for its pyramids. 填空题：The ____46. 选择题：Which day comes after Monday?A. SundayB. TuesdayC. WednesdayD. Thursday47. 填空题：The __________ (冷战) led to the space race between the USA and USSR.48. 填空题：The __________ is a famous city known for its modern architecture. (迪拜)49. 选择题：How many months are there in a year?A. TenB. TwelveC. ElevenD. Nine50. 选择题：What is the capital of Norway?A. OsloB. BergenC. TrondheimD. Stavanger答案:A51. 选择题：What do we call the study of living organisms?A. BiologyB. ChemistryC. PhysicsD. Geology答案:A52. 听力题：I have a ___ of stickers. (sheet)53. 选择题：What do you call the time when the sun is highest in the sky?A. DawnB. NoonC. DuskD. Midnight答案:B54. 选择题：What do you call a person who repairs cars?A. MechanicB. EngineerC. TechnicianD. Designer答案:A55. 填空题：A _____ (章鱼) can change its shape to fit through tight spaces.56. 听力题：The chemical formula for manganese dioxide is _______.57. 填空题：The __________ is a famous mountain range in Europe. (阿尔卑斯山)58. 听力题：A meteor shower occurs when Earth passes through ______.59. 选择题：What is the term for a person who studies rocks?A. GeologistB. BiologistC. ArcheologistD. Chemist答案:A60. 听力题：Chlorine is a type of _______ that can be harmful.61. 选择题：What is the main purpose of a compass?A. Measure temperatureB. Find directionC. Tell timeD. Check altitude62. 填空题：A cow gives us _________ (牛奶).I like to collect ________ (邮票) from different places.64. 填空题：I saw a ______ (青蛙) jumping in the pond.65. 填空题：I hear the sound of ______ (雷声) in the distance.66. 听力题：A chemical change may involve a change in _____ (color, temperature, or odor).67. 填空题：The ________ was a landmark event in the quest for equality.68. 选择题：What is the name of the famous landmark in Brazil?A. Christ the RedeemerB. Statues of Easter IslandC. Great WallD. Eiffel Tower答案: A69. 选择题：What is the capital of Serbia?A. BelgradeB. Novi SadC. NišD. Kragujevac答案: A70. 填空题：My sister is passionate about __________ (科学).71. 填空题：The __________ (历史的交融) creates understanding.72. 听力题：__________ are used in the cleaning industry for stain removal.73. 听力题：Deltas are often home to diverse ______ species.I like to write ______ (科技) articles to share knowledge with others. It’s a great way to inform people.75. 听力题：The chemical formula for manganese sulfate is _______.76. 听力题：The molecule responsible for carrying oxygen in the blood is ______.77. 选择题：What do we call the science of studying insects?A. EntomologyB. ZoologyC. BotanyD. Ecology答案:A78. 填空题：The __________ (历史的见证) offers insight into human behavior.79. 听力题：The process of making vinegar involves fermentation of _______.80. 填空题：This boy, ______ (这个男孩), loves to play basketball after school.81. 填空题：The _____ (植物) can grow in various climates.82. 听力题：She has a ___ (big/small) smile.83. 听力题：The _______ of light can be reflected off surfaces.84. 听力题：A __________ is an area of land that is very dry.85. 选择题：What is the name of the fairy tale character who had long hair?A. CinderellaB. RapunzelC. BelleD. Ariel答案:BWhat is the term for a baby cow?A. CalfB. FoalC. LambD. Kid答案:A87. 填空题：The city of Venice is known for its ________ (运河).88. 听力题：The ______ is where we live on Earth.89. 选择题：What do we call the first meal of the day?A. LunchB. DinnerC. BreakfastD. Snack90. 填空题：I like to draw pictures of ______ (天气).91. 选择题：How many sides does an octagon have?A. 6B. 7C. 8D. 9答案:C92. 听力题：The door is ___. (open)93. 听力题：A force can change an object’s ______.94. 听力题：The study of Earth's geological history is crucial for understanding ______ changes.95. 选择题：What is the name of the plant that grows in deserts?A. CactusB. FernC. RoseD. Oak96. 听力题：The capital city of Bhutan is __________.97. 填空题：The weather can change very ______ (快).98. 选择题：What is the name of the famous ancient city in Egypt?A. CairoB. AlexandriaC. ThebesD. All of the above99. 填空题：The pelican has a big _________ (嘴巴).100. 填空题：I enjoy _______ (参加) sports competitions.。

小学上册第5次英语第5单元真题(有答案)

小学上册第5次英语第5单元真题(有答案)

小学上册英语第5单元真题(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.He is fishing in the ___. (river)2. A __________ (栽培技巧) can lead to better harvests.3.What is the color of grass?A. BlueB. GreenC. YellowD. Brown答案:B4.The _____ (冬季) can be harsh for some plants.5.My neighbor is a ______. He enjoys gardening.6.The ________ (环境影响评估) guides actions.7.What is the opposite of "big"?A. SmallB. TallC. ThinD. Wide答案:A Small8.The __________ is essential for breathing and respiration.9.Rockets are used to launch spacecraft into ______.10.The ________ has a long tail.11.The process of electrolysis uses electricity to cause a _____ reaction.12.The _____ (果实) of the apple tree is delicious and sweet.13.We should _______ (关注)健康问题。

14.What is 15 divided by 5?A. 2B. 3C. 4D. 5答案: B15.When ice melts, it turns into __________.16.I planted a _____ (果树) in my garden.17.My uncle is my funny _______ who tells the best jokes ever.18. A neutron is found in the _____ of an atom.19.The __________ can reveal trends in climate change.20.We have a ______ (丰富的) variety of activities at school.21.I enjoy making crafts with my ________ (姐妹) using recycled materials.22.The main product of the Calvin cycle is ______.23.The _______ (鹿) has antlers.24. A volcano erupts when ______ comes to the surface.25.选词填空,将词语写在四线三格内。

小学上册第十三次英语第4单元测验试卷

小学上册第十三次英语第4单元测验试卷

小学上册英语第4单元测验试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.My ________ (玩具名称) has a pretty dress.2.My _____ (玩具火车) chugs around the track.3.The leaves fall gracefully from the _______ in autumn.4.The kitten is ______ with a ball of yarn. (playing)5.Which word means "happy"?A. SadB. JoyfulC. AngryD. Scared6.I can ________ (swim) in the pool.7.What is the capital of Norway?A. OsloB. BergenC. TrondheimD. Stavanger8. A _______ is a representation of a chemical reaction using symbols.9.We are going to the ___. (fair) this weekend.10.The concept of climate mitigation focuses on reducing the impacts of ______ change.11.We have a _____ (庆典) in town.12.The capital city of Bhutan is __________.13. A __________ is a reaction that produces solid precipitates.14.The garden is full of _______ that bloom in different colors.15.The chemical formula for gadolinium oxide is _____.16.The symbol for selenium is _____.17.The rabbit can be very _______ (友好) with children.18.We are going to ______ a movie tonight. (watch)19.What do we call the outer layer of the Earth?A. CoreB. MantleC. CrustD. Atmosphere答案:C20.The ______ (小鱼) swims gracefully in the aquarium.21. A strong base has a pH value greater than _______.22.What do we call a place where we can see animals?A. ZooB. FarmC. AquariumD. All of the above23._____ (landscaping) improves outdoor spaces.24.What do you call a baby kangaroo?A. JoeyB. CalfC. KitD. Pup答案:A25. A chemical change can be identified by color ______.26.She is ___ her bike. (riding)27.I have a collection of ________ (漫画书) that I read during my free time. They are so ________ (有趣).28.My favorite type of ________ (食物) is sushi.29.What is 5 2?A. 3B. 4C. 2D. 1答案:A30.What do we call the part of the plant that absorbs sunlight?A. StemB. LeafC. FlowerD. Root答案:B31. A ______ is a collection of data gathered from observations.32.I can draw a picture of my favorite _________ (玩具) and share it with my class.33.My dad is a fantastic __________ (模范) for our family.34.What do we call a young person in school?A. StudentB. ScholarC. LearnerD. Pupil35.The _____ (guitar) sounds nice.36.The _____ (raspberry) plant produces sweet berries.37.I like to go camping in the ______ (森林) and explore nature. It’s a great way to relax and unwind.38.The __________ (历史的价值观差异) can lead to conflict.39.The __________ is cool and refreshing during the summer. (海洋)40.I have a toy _____ that can jump.41.What do you call the process of a caterpillar becoming a butterfly?A. MetamorphosisB. EvolutionC. TransformationD. Development答案:A42.My ______ is very inspiring and motivates others.43.She is a great ________.44.I enjoy _______ (在公园散步).45.I enjoy ______ (reading) comics.46.What is the main ingredient in salad?A. PastaB. LettuceC. RiceD. Bread47.I love to eat ______ during the summer.48.I want to ________ (support) local causes.49.She is _______ (climbing) the ladder.50.What is the name of the famous explorer who discovered America?A. Ferdinand MagellanB. Christopher ColumbusC. Marco PoloD. Vasco da Gama答案:B51.The Earth's atmosphere is crucial for protecting ______ life.52.The _______ of light can be tested by using a variety of filters.53.The chemical formula for sodium thiocyanate is _____.54.We have _____ (很多) fun games.55.War was a period of tension between the _______ and the Soviet Union. (美国) The Cold56.I like to ______ (参与) in local campaigns.57.What is the capital of South Africa?A. PretoriaB. JohannesburgC. Cape TownD. Durban答案:A Pretoria58. A _______ is a reaction that occurs in the earth's crust.59.natural disaster) can cause severe damage to areas. The ____60.The chemical symbol for manganese is ______.61.My favorite snack is ________ and cheese.62.Ants work together to build a ________________ (巢).63.My ____ likes to be dressed up in different outfits. (玩具名称)64.The capital of Kosovo is ________ (普里什蒂纳).65.I saw a _______ (小刺猬) in the garden.66.Which animal is known for its long neck?A. ElephantB. GiraffeC. LionD. Kangaroo67. A _______ can enhance indoor spaces.68.Countries are divided into smaller regions called ________.69.The ________ was a significant period in the history of Europe.70.Which animal is known for its long neck?A. ElephantB. GiraffeC. LionD. Tiger答案:B71.What is the main function of the stomach?A. To pump bloodB. To digest foodC. To filter wasteD. To store energy答案:B72.He is reading a ___. (story)73.What do we call a scientist who studies the universe?A. AstronomerB. AstrophysicistC. CosmologistD. Geologist答案:A74.Vegetables like carrots grow _____ (在地下).75.The fish is _____ in the tank. (swimming)76.The museum has _______ (很多展品).77.The __________ (种植计划) is essential for successful gardening.78.I like to bake ______ (蛋糕) for special occasions. Decorating them is my favorite part!79. A solar flare is a sudden eruption of energy on the sun’s ______.80.The chemical symbol for iridium is _____.81.What is the main ingredient in risotto?A. RiceB. PastaC. BarleyD. Quinoa答案:A82.What is the name of the famous statue in Rio de Janeiro?A. Christ the RedeemerB. Statue of LibertyC. DavidD. The Thinker答案:A83.What is the name of the famous singer known for "Like a Rolling Stone"?A. Elton JohnB. Bob DylanC. Bruce SpringsteenD. Johnny Cash答案:B84.The Earth's atmosphere is composed mainly of nitrogen and ______.85. A solution is a mixture where one substance is dissolved in ________.86.The goldfish has _______ (眼睛) that help it see.87.The substance that is dissolved in a solution is called a ______.88.What do we call a traditional story that explains something in nature?A. MythB. FableC. LegendD. Tale89.The ______ is an important predator.90.My ________ (玩具) is very colorful and bright.91. A cat's agility helps it catch ______ (猎物).92.The trees in the _______ provide shade and a place to relax.93.My friend’s dad, ______ (我朋友的爸爸), is a businessman.94. A ______ often forages for food.95._____ (春天) is when many plants start to bloom.96.My cousin is very __________ (乐观).97.What do we call a person who studies ancient texts?A. PhilologistB. LinguistC. HistorianD. Archeologist答案:A98.What do we use to cut paper?A. ScissorsB. TapeC. GlueD. Ruler答案:A99.What do you call the time when the sun rises?A. DawnB. DuskC. MidnightD. Afternoon答案:A100.What is the name of the famous river that runs through Egypt?A. NileB. AmazonC. MississippiD. Yangtze。

On the Decay of the Art of Lying

On the Decay of the Art of Lying

On the Decay of the Art of Lying by Mark Twain [Sameul Clemens]ESSAY, FOR DISCUSSION, READ AT A MEETING OF THE HISTORICALAND ANTIQUARIAN CLUB OF HARTFORD, AND OFFERED FOR THETHIRTY-DOLLAR PRIZE.[*][*] Did not take the prize.Observe, I do not mean to suggest that the _custom_ of lying has suffered any decay or interruption--no, for the Lie, as a Virtue, A Principle, is eternal; the Lie, as a recreation, a solace, a refuge in time of need, the fourth Grace, the tenth Muse, man's best and surest friend, is immortal, and cannot perish from the earth while this club remains. My complaint simply concerns the decay of the _art_ of lying. No high-minded man, no man of right feeling, can contemplate the lumbering and slovenly lying of the present day without grieving to see a noble art so prostituted. In this veteran presence Inaturally enter upon this theme with diffidence; it is like an old maid trying to teach nursery matters to the mothers in Israel. It would not become to me to criticise you, gentlemen--who are nearly all myelders--and my superiors, in this thing--if I should here and there _seem_ to do it, I trust it will in most cases be more in a spirit of admiration than fault-finding; indeed if this finest of the fine arts had everywhere received the attention, the encouragement, and conscientious practice and development which this club has devoted to it, I should not need to utter this lament, or shred a single tear.I do not say this to flatter: I say it in a spirit of just and appreciative recognition. [It had been my intention, at this point, to mention names and to give illustrative specimens, but indications observable about me admonished me to beware of the particulars and confine myself to generalities.]No fact is more firmly established than that lying is a necessity of our circumstances--the deduction that it is then a Virtue goes without saying.No virtue can reach its highest usefulness without careful and diligent cultivation--therefore, it goes without saying that this one ought to be taught in the public schools--even in the newspapers. What chance has the ignorant uncultivated liar against the educated expert? What chance have Iagainst Mr. Per--against a lawyer? _Judicious_lying is what the world needs.I sometimes think it were even better and safer not to lie at all than to lie injudiciously. An awkward, unscientific lie is often as ineffectual as the truth.Now let us see what the philosophers say. Note that venerable proverb:Children and fools _always_ speak the truth. The deduction is plain--adults and wise persons _never_speak it. Parkman, the historian, says, "The principle of truth may itself be carried into an absurdity." In another place in the same chapters he says, "The saying is old that truth should not be spoken at all times; and those whom a sick conscience worries into habitual violation of the maxim are imbeciles and nuisances." It is strong language, but true. None of us could _live_ with an habitual truth-teller; but thank goodness none of us has to. An habitual truth-teller is simply an impossible creature; he does not exist; he never has existed. Of course there are people who _think_ they never lie, but it is not so--and this ignorance is one of the very things that shame our so-called civilization. Everybody lies--every day; every hour;awake; asleep; in his dreams; in his joy; in hismourning; if he keeps his tongue still, his hands, his feet, his eyes, his attitude, will convey deception--and purposely. Even in sermons--but that is a platitude.In a far country where I once lived the ladies used to go around paying calls, under the humane and kindly pretence of wanting to see each other;and when they returned home, they would cry out with a glad voice, saying, "We made sixteen calls and found fourteen of them out"--not meaning that they found out anything important against the fourteen--no, that was only a colloquial phrase to signify that they were not at home--and their manner of saying it expressed their lively satisfaction in that fact. Now their pretence of wanting to see the fourteen--and the other two whom they had been less lucky with--was that commonest and mildest form of lying which is sufficiently described as a deflection from the truth. Is it justifiable?Most certainly. It is beautiful, it is noble; for its object is, _not_ to reap profit, but to convey a pleasure to the sixteen. The iron-souled truth-monger would plainly manifest, or even utter the fact that he didn't want to see those people--and he would be an ass, and inflict totally unnecessary pain.And next, those ladies in that far country--but never mind, they had a thousand pleasant ways of lying, that grew out of gentle impulses, and were a credit to their intelligence and an honor to their hearts. Let the particulars go.The men in that far country were liars, every one. Their mere howdy-do was a lie, because _they_ didn't care how you did, except they were undertakers. To the ordinary inquirer you lied in return; for you made no conscientious diagnostic of your case, but answered at random, and usually missed it considerably. You lied to the undertaker, and said your health was failing--a wholly commendable lie, since it cost you nothing and pleased the other man.If a stranger called and interrupted you, you said with your hearty tongue, "I'm glad to see you," and said with your heartier soul, "I wish you were with the cannibals and it was dinner-time." When he went, you said regretfully, "_Must_ you go?" and followed it with a "Call again;" but you did no harm, for you did not deceive anybody nor inflict any hurt, whereas the truth would have made you both unhappy.I think that all this courteous lying is a sweet and loving art, and should be cultivated. The highestperfection of politeness is only a beautiful edifice, built, from the base to the dome, of graceful and gilded forms of charitable and unselfish lying.What I bemoan is the growing prevalence of the brutal truth. Let us do what we can to eradicate it. An injurious truth has no merit over an injurious lie.Neither should ever be uttered. The man who speaks an injurious truth lest his soul be not saved if he do otherwise, should reflect that that sort of a soul is not strictly worth saving. The man who tells a lie to help a poor devil out of trouble, is one of whom the angels doubtless say, "Lo, here is an heroic soul who casts his own welfare in jeopardy to succor his neighbor's;let us exalt this magnanimous liar."An injurious lie is an uncommendable thing; and so, also, and in the same degree, is an injurious truth--a fact that is recognized by the law of libel.Among other common lies, we have the _silent_ lie--the deception which one conveys by simply keeping still and concealing the truth. Many obstinate truth-mongers indulge in this dissipation, imagining that if they _speak_ no lie, they lie not at all. In that far country where I once lived, there was a lovelyspirit, a lady whose impulses were always high and pure, and whose character answered to them. One day I was there at dinner, and remarked, in a general way, that we are all liars. She was amazed, and said, "Not _all_?"It was before "Pinafore's" time. so I did not make the response which would naturally follow in our day, but frankly said, "Yes, _all_--we are all liars.There are no exceptions." She looked almost offended, "Why, do you include _me_?" "Certainly," I said. "I think you even rank as an expert." She said "Sh-'sh! the children!" So the subject was changed in deference to the children's presence, and we went on talking about other things. But as soon as the young people were out of the way, the lady came warmly back to the matter and said, "I have made a rule of my life to never tell a lie; and Ihave never departed from it in a single instance."I said, "I don't mean the least harm or disrespect, but really you have been lying like smoke ever since I've been sitting here. It has caused me a good deal of pain, because I'm not used to it." She required of me an instance--just a single instance.So I said--"Well, here is the unfilled duplicate of the blank,which the Oakland hospital people sent to you by the hand of the sick-nurse when she came here to nurse your little nephew through his dangerous illness. This blank asks all manners of questions as to the conduct of that sick-nurse: 'Did she ever sleep on her watch? Did she ever forget to give the medicine?' and so forth and so on. You are warned to be very careful and explicit in your answers, for the welfare of the service requires that the nurses be promptly fined or otherwise punished for derelictions. You told me you were perfectly delighted with this nurse--that she had a thousand perfections and only one fault: you found you never could depend on her wrapping Johnny up half sufficiently while he waited in a chilly chair for her to rearrange the warm bed.You filled up the duplicate of this paper, and sent it back to the hospital by the hand of the nurse. How did you answer this question--'Was the nurse at any time guilty of a negligence which was likely to result in the patient's taking cold?' Come--everything is decided by a bet here in California: ten dollars to ten cents you lied when you answered that question." She said, "Ididn't; _I left it blank!_" "Just so--you have tolda _silent_ lie; you have left it to be inferred that you had no fault to find in that matter." She said, "Oh, was that a lie? And _how_ could I mention her one single fault, and she is so good?--It would have been cruel."I said, "One ought always to lie, when one can do good by it; your impulse was right, but your judgment was crude;this comes of unintelligent practice. Now observe the results of this inexpert deflection of yours. You know Mr. Jones's Willie is lying very low with scarlet-fever; well, your recommendation was so enthusiastic that that girl is there nursing him, and the worn-out family have all been trustingly sound asleep for the last fourteen hours, leaving their darling with full confidence in those fatal hands, because you, like young George Washington, have a reputa--However, if you are not going to have anything to do, I will come around to-morrow and we'll attend the funeral together, for, of course, you'll naturally feel a peculiar interest in Willie's case--as personal a one, in fact, as the undertaker."But that was not all lost. Before I was half-way through she was in a carriage and making thirty milesan hour toward the Jones mansion to save what was left of Willie and tell all she knew about the deadly nurse. All of which was unnecessary, as Willie wasn't sick;I had been lying myself. But that same day, all the same, she sent a line to the hospital which filled up the neglected blank, and stated the _facts,_ too, in the squarest possible manner.Now, you see, this lady's fault was _not_ in lying, but in lying injudiciously. She should have told the truth, _there,_ and made it up to the nurse with a fraudulent compliment further along in the paper. She could have said, "In one respect this sick-nurse is perfection--when she is on the watch, she never snores." Almost any little pleasant lie would have taken the sting out of that troublesome but necessary expression of the truth.Lying is universal--we _all_ do it. Therefore, the wise thing is for us diligently to train ourselves to lie thoughtfully, judiciously; to lie with a good object, and not an evil one; to lie for others' advantage, and not our own; to lie healingly, charitably, humanely, not cruelly, hurtfully, maliciously; to lie gracefully and graciously, not awkwardly and clumsily;to lie firmly, frankly, squarely, with head erect,not haltingly, tortuously, with pusillanimous mien, as being ashamed of our high calling. Then shall we be rid of the rank and pestilent truth that is rotting the land; then shall we be great and good and beautiful, and worthy dwellers in a world where even benign Nature habitually lies, except when she promises execrable weather.Then--But am I but a new and feeble student in this gracious art; I cannot instruct _this_ club.Joking aside, I think there is much need of wise examination into what sorts of lies are best and wholesomest to be indulged, seeing we _must_ all lie and we _do_ all lie, and what sorts it may be best to avoid--and this is a thing which I feel I can confidently put into the hands of this experienced Club--a ripe body, who may be termed, in this regard, and without undue flattery, Old Masters.End11。