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Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’and the dark scalar mediatorΦ.The total cross-sections and various differential distributions of the processes e+e-→qqA’and e+e→qqφ(q=u,d,c,s and b quarks)are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify(or exclude)the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future CEPC experiment with s1/2=91.2 GeV and 240 GeV.With CEPC running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon(20 GeV相似文献
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Heavy charged gauge bosons are proposed in some theories beyond the standard model. We explore the discovery potential for W →tb with top quark semi-leptonic decay at the LHC. We concentrate on the new physics signal search with the deviation from the standard model prediction if the resonance peak of W cannot be observed directly. Signal events with two jets plus one charged lepton and missing energy are simulated, together with the dominant standard model backgrounds. In this paper, it is found that suitable cuts on the kinematic observables can effectively suppress the standard model backgrounds, so that it is possible to search for a W signal at the LHC if its mass is less than 6.6 Te V. 相似文献
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We calculate the masses of the QQqq(Q=c,b:q=u,d,s)tetraquark states with the aid of heavy diquark-antiquark symmetry(HDAS)and the chromomagnetic interaction(CMI)model.The masses of the highestspin(J=2)tetraquarks that have only the(QQ)(3):(qq)3.color structure are related with those of conventional hadrons using HDAS.Thereafter,the masses of their partner states are determined with the mass splittings in the CMI model.Our numerical results reveal that(i)the lightest ccnn(n=u,d)is an I(JP)=0(1+)state around 3929 MeV(53 MeV above the DD* threshold),and none of the double-charm tetraquarks are stable;(ii)the stable double-bottom tetraquarks are the lowest 0(1+)bbin around 10488 MeV(≈116 MeV below the BB*threshold)and the lowest 1/2(1+)bbns around 10671 MeV(≈20 MeV below the BBs*/BsB*threshold);and(iii)the two lowest bcnn tetraquarks,namely the lowest 0(0+)around 7167 MeV and the lowest 0(1)around 7223 MeV,are in the nearthreshold states.Moreover,we discuss the constraints on the masses of double-heavy hadrons.Specifically,for the lowest nonstrange tetraquarks,we obtain Tcc<3965 MeV,Tbb<10627 MeV,and Tbc<7199 MeV. 相似文献
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研究了e^ e^-湮没中“初始”轻夸克和胶子劈裂产生的e^-组合为D^-介子(包括D^-,Ds^-,D^-0)或D^-*介子(包括D*^-,Ds^*-,D^-*0)的过程.发现尤其在√s=Mz处,其产额相对较大,当限制D^-或D^-*的能量大于20GeV时,它和c夸克碎裂产物的不变质量谱在稍大于2MD^-附近有一个峰,这是该过程区别于其它D^-或^-*介子产生过程的显著特征.此过程产生的矢量介子基本上是纵向极化的,与实验上观测到的D^-*介子的纵向极化一致. 相似文献
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We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e~+e~-collision.The pentaquark production at B factory energy is dominated by e~+e~-→ccg→P_c+X,while at Z~0pole energy,there are several partonic processes playing significant role.Our results show that it is possible to search for the direct pentaquark production signal at e~+e~-colliders,which is important to understand the properties of pentaquark. 相似文献
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