The potential for detecting the lepton flavor changing neutral current (LFCNC) via the Z → eτ rare decay at a Z-factory is investigated.Practicable event selection strategies are designed to increase signal signific...The potential for detecting the lepton flavor changing neutral current (LFCNC) via the Z → eτ rare decay at a Z-factory is investigated.Practicable event selection strategies are designed to increase signal significance over SM contributions.Assuming no apparent deviation from SM predictions,one can conclude that the most general model-independent LFCNC effective form factors would be constrained at an unprecedent level,and accordingly a 3-order improvement from LEP1 measurements on the upper limit of BR(Z → eτ) could be achieved,as precisely as 10-8 with 100 fb-1 at Z-factory.展开更多
To test the standard model(SM)precisely and to look for the clues deviating from SM,a proposal for determining the effective electro-weak mixing angles sin2θefff(particularly f=lept,c,b)is proposed.It is via observin...To test the standard model(SM)precisely and to look for the clues deviating from SM,a proposal for determining the effective electro-weak mixing angles sin2θefff(particularly f=lept,c,b)is proposed.It is via observing the asymmetries(the forward-backward one AFB,the left-right one ALR and the combined left-right forward-backward one ALRFB)of the doubly heavy-flavored hadrons in the production at a super Z-factory(an e+e-collider designed with a luminosity as high as possible for modernday techniques runs around the center-of-mass energy s1/2=mZ).To see the sensitivity,uncertainties as well as the event accumulation precisely,the observables for describing the asymmetries of the produced hadrons are computed numerically with varying effective mixing angles,and based on the result analyses,it is concluded that the proposal may offer an independent complement determination of the effective mixing angles.展开更多
Considering the possibility to build an e + e-collider at the energies around Z-boson resonance with a luminosity so high as L ∝ 10 34 cm-2 s-1 (even higher) and the abilities of a modern synthesis detector,we system...Considering the possibility to build an e + e-collider at the energies around Z-boson resonance with a luminosity so high as L ∝ 10 34 cm-2 s-1 (even higher) and the abilities of a modern synthesis detector,we systematically calculate the exclusive two body processes of the heavy quarkonium production: e + eannihilates into a heavy quarkonium and a photon,involving the initial state radiation (i.e.ISR) cases,at the energies around the Z-boson resonance.Since the couplings of Z-boson to quarks contain an axial vector term as well as a vector one,a charmonium such as J/ψ or η c or h c or χ cJ ···,or a bottomonium such as Υ or η b or h b or χ bJ ···,associating with a photon,may be produced respectively via Z-boson annihilation.If we call such a collider with so high luminosity and running around the Z-boson resonance as a Z-factory,then our results obtained here indicate that experimental studies of the various heavy quarkona (their ground and excited states) via the two-body processes at a Z-factory have outstanding advantages,especially,the production of the possible states with quantum numbers J PC = 1-via ISR.展开更多
文摘The potential for detecting the lepton flavor changing neutral current (LFCNC) via the Z → eτ rare decay at a Z-factory is investigated.Practicable event selection strategies are designed to increase signal significance over SM contributions.Assuming no apparent deviation from SM predictions,one can conclude that the most general model-independent LFCNC effective form factors would be constrained at an unprecedent level,and accordingly a 3-order improvement from LEP1 measurements on the upper limit of BR(Z → eτ) could be achieved,as precisely as 10-8 with 100 fb-1 at Z-factory.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275036,11745006,11535002,11821505,11675239,11705045,11821505,and 11805140)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDY-SSWSYS006)。
文摘To test the standard model(SM)precisely and to look for the clues deviating from SM,a proposal for determining the effective electro-weak mixing angles sin2θefff(particularly f=lept,c,b)is proposed.It is via observing the asymmetries(the forward-backward one AFB,the left-right one ALR and the combined left-right forward-backward one ALRFB)of the doubly heavy-flavored hadrons in the production at a super Z-factory(an e+e-collider designed with a luminosity as high as possible for modernday techniques runs around the center-of-mass energy s1/2=mZ).To see the sensitivity,uncertainties as well as the event accumulation precisely,the observables for describing the asymmetries of the produced hadrons are computed numerically with varying effective mixing angles,and based on the result analyses,it is concluded that the proposal may offer an independent complement determination of the effective mixing angles.
基金supported in part by the National Natural Science Foundation of China (Grant Nos.10805082,10875155,10847001,10875155 and 10775141)the Natural Science Foundation Project of CQ CSTC (Grant No.2008BB0298)supported in part by the Project of Knowledge Innovation Program (PKIP) of Chinese Academy of Sciences (Grant No.KJCX2.YW.W10)
文摘Considering the possibility to build an e + e-collider at the energies around Z-boson resonance with a luminosity so high as L ∝ 10 34 cm-2 s-1 (even higher) and the abilities of a modern synthesis detector,we systematically calculate the exclusive two body processes of the heavy quarkonium production: e + eannihilates into a heavy quarkonium and a photon,involving the initial state radiation (i.e.ISR) cases,at the energies around the Z-boson resonance.Since the couplings of Z-boson to quarks contain an axial vector term as well as a vector one,a charmonium such as J/ψ or η c or h c or χ cJ ···,or a bottomonium such as Υ or η b or h b or χ bJ ···,associating with a photon,may be produced respectively via Z-boson annihilation.If we call such a collider with so high luminosity and running around the Z-boson resonance as a Z-factory,then our results obtained here indicate that experimental studies of the various heavy quarkona (their ground and excited states) via the two-body processes at a Z-factory have outstanding advantages,especially,the production of the possible states with quantum numbers J PC = 1-via ISR.