The single charged top-pion production processes e~+ e~- → tbΠ_t~- and e~+e~- → W~+Π_t~- are studied in the framework of top-color-assisted technicolor (TC2) model. Ourstudies show that the cross section σ(e~+ e...The single charged top-pion production processes e~+ e~- → tbΠ_t~- and e~+e~- → W~+Π_t~- are studied in the framework of top-color-assisted technicolor (TC2) model. Ourstudies show that the cross section σ(e~+ e~- → tbΠ_t~-) Teaches the level of tens of fb andσ(e~+ e~- → W~+Π_t~-) reaches the level of a few fb. With the yearly integrated luminosity of ￡～ 500 fb~(-1) expected at the planned colliders, one could collect thousands of charged top-pion ofevents via the process e~+ e~- → tbΠ_t~- and hundreds of events via the process e~+ e~- →W~+Π_t~-. The flavor changing decay mode Π_t~- → bc is the best channel to detect chargedtop-pion due to the clean SM background. With a large number of events and the clean background, thecharged top-pion should be observable at the planned colliders. Therefore, our studies in thispaper can help us to search for charged top-pion, and furthermore, to test the TC2 model.展开更多
In this paper we investigate the effects of the large extra dimensions on the two processes e＋ e-→＋ H^0 Z^0 Z^0 and e^＋e^-→ H^0H^0 Z^0 at linear colliders in both unpolarized and polarized collision modes. We fin...In this paper we investigate the effects of the large extra dimensions on the two processes e＋ e-→＋ H^0 Z^0 Z^0 and e^＋e^-→ H^0H^0 Z^0 at linear colliders in both unpolarized and polarized collision modes. We find that the virtual Kaluza-Klein graviton exchange can significantly enhance the cross section from their standard model expectations for these two processes. The results show that the LED effect on the process e＋ e-→＋ H^0 Z^0 Z^0 allows the observation limits on the effective scale Ms to be probed up to 9. 75 TeV and 10.1 TeV in the unpolarized and ＋-（λe＋ =1/2, λe-= -1/2） polarized beam collision modes （with Pe＋ = 0.6, Pe-=0.8）, respectively. For the process e＋ e-→＋ H^0 H^0 Z^0, these limits on Ms can be probed up to 6.06 TeV and 6.38 TeV in the unpolarized and polarized collision modes separately. We find that the λe＋ = 1/2, λe-= -1/2 polarization collision mode in both processe＋ e-→＋ H^0 Z^0 Z^0 and e＋ e-→＋ H^0 H^0 Z^0 may provide a possibility to improve the sensitivity in probing the LED effects.展开更多
The top-pair production in association with a Z^0-boson at a photon-photon collider is an important process in probing the coupling between top-quarks and vector boson and discovering the signature of possible new phy...The top-pair production in association with a Z^0-boson at a photon-photon collider is an important process in probing the coupling between top-quarks and vector boson and discovering the signature of possible new physics. We describe the impact of the complete supersymmetric QCD （SQCD） next-to-leading order （NLO） radiative corrections on this process at a polarized or unpolarized photon collider, and make a comparison between the effects of the SQCD and the standard model （SM） QCD. We investigate the dependence of the lowest-order （LO） and QCD NLO corrected cross sections in both the SM and minimal supersymmetric standard model （MSSM） on colliding energy √s in different polarized photon collision modes. The LO, SM NLO, and SQCD NLO corrected distributions of the invariant mass of tt^--pair and the transverse momenta of final Z^0-boson are presented. Our numerical results show that the pure SQCD effects in γγ →tt^- Z^0 process can be more significant in the ＋＋ polarized photon collision mode than in other collision modes, and the relative SQCD radiative correction in unpolarized photon collision mode varies from 32.09% to -1.89% when √s goes up from 500 GeV to 1.5 TeV.展开更多
In the SU（3） simple group model, the new neutral gauge boson Z＇ couples to pairs of SM fermions with couplings fixed in terms of the SM gauge couplings and depending only on the choice of the fermion embedding. In ...In the SU（3） simple group model, the new neutral gauge boson Z＇ couples to pairs of SM fermions with couplings fixed in terms of the SM gauge couplings and depending only on the choice of the fermion embedding. In this paper, we calculate the contributions of this new particle to the processes e^＋e^-→l^＋l^-, bb^-, and cc^- and study the possibility of detecting this new particle via these processes in the future high-energy linear e^＋e^- collider（LC） experiments with √s= 500 GeV and ￡int= 340 fb^-1. We find that the new gauge boson Z＇ is most sensitive to the process e^＋e^-→b^＋b^-. As long as Mz,≤2 TeV , the absolute values of the relative correction parameter are larger than 5%. We calculate the forward-backward asymmetries and left-right asymmetries for the process e^＋e^-→c^＋c^-, with both the universal and anomaly-free fermion embeddings. Bounds on Z＇ masses are also estimated within 95% confidence level.展开更多
基金国家自然科学基金，河南省教育厅优秀青年基金，the Henan Innovation Project for University Prominent Research Talents
文摘The single charged top-pion production processes e~+ e~- → tbΠ_t~- and e~+e~- → W~+Π_t~- are studied in the framework of top-color-assisted technicolor (TC2) model. Ourstudies show that the cross section σ(e~+ e~- → tbΠ_t~-) Teaches the level of tens of fb andσ(e~+ e~- → W~+Π_t~-) reaches the level of a few fb. With the yearly integrated luminosity of ￡～ 500 fb~(-1) expected at the planned colliders, one could collect thousands of charged top-pion ofevents via the process e~+ e~- → tbΠ_t~- and hundreds of events via the process e~+ e~- →W~+Π_t~-. The flavor changing decay mode Π_t~- → bc is the best channel to detect chargedtop-pion due to the clean SM background. With a large number of events and the clean background, thecharged top-pion should be observable at the planned colliders. Therefore, our studies in thispaper can help us to search for charged top-pion, and furthermore, to test the TC2 model.
基金The project supported in part by National Natural Science Foundation of China and the Special Fund of the Chinese Academy of Sciences
文摘In this paper we investigate the effects of the large extra dimensions on the two processes e＋ e-→＋ H^0 Z^0 Z^0 and e^＋e^-→ H^0H^0 Z^0 at linear colliders in both unpolarized and polarized collision modes. We find that the virtual Kaluza-Klein graviton exchange can significantly enhance the cross section from their standard model expectations for these two processes. The results show that the LED effect on the process e＋ e-→＋ H^0 Z^0 Z^0 allows the observation limits on the effective scale Ms to be probed up to 9. 75 TeV and 10.1 TeV in the unpolarized and ＋-（λe＋ =1/2, λe-= -1/2） polarized beam collision modes （with Pe＋ = 0.6, Pe-=0.8）, respectively. For the process e＋ e-→＋ H^0 H^0 Z^0, these limits on Ms can be probed up to 6.06 TeV and 6.38 TeV in the unpolarized and polarized collision modes separately. We find that the λe＋ = 1/2, λe-= -1/2 polarization collision mode in both processe＋ e-→＋ H^0 Z^0 Z^0 and e＋ e-→＋ H^0 H^0 Z^0 may provide a possibility to improve the sensitivity in probing the LED effects.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.10575094 and 10875112the National Science Fund for Fostering Talents in Basic Science under Grant No.J0630319+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) under Grant No.20050358063a Special Fund Sponsored by Chinese Academy of Sciences
文摘The top-pair production in association with a Z^0-boson at a photon-photon collider is an important process in probing the coupling between top-quarks and vector boson and discovering the signature of possible new physics. We describe the impact of the complete supersymmetric QCD （SQCD） next-to-leading order （NLO） radiative corrections on this process at a polarized or unpolarized photon collider, and make a comparison between the effects of the SQCD and the standard model （SM） QCD. We investigate the dependence of the lowest-order （LO） and QCD NLO corrected cross sections in both the SM and minimal supersymmetric standard model （MSSM） on colliding energy √s in different polarized photon collision modes. The LO, SM NLO, and SQCD NLO corrected distributions of the invariant mass of tt^--pair and the transverse momenta of final Z^0-boson are presented. Our numerical results show that the pure SQCD effects in γγ →tt^- Z^0 process can be more significant in the ＋＋ polarized photon collision mode than in other collision modes, and the relative SQCD radiative correction in unpolarized photon collision mode varies from 32.09% to -1.89% when √s goes up from 500 GeV to 1.5 TeV.
基金supported in part by a grant from Henan Institute of Science and Technology under Grant No.06040
文摘In the SU（3） simple group model, the new neutral gauge boson Z＇ couples to pairs of SM fermions with couplings fixed in terms of the SM gauge couplings and depending only on the choice of the fermion embedding. In this paper, we calculate the contributions of this new particle to the processes e^＋e^-→l^＋l^-, bb^-, and cc^- and study the possibility of detecting this new particle via these processes in the future high-energy linear e^＋e^- collider（LC） experiments with √s= 500 GeV and ￡int= 340 fb^-1. We find that the new gauge boson Z＇ is most sensitive to the process e^＋e^-→b^＋b^-. As long as Mz,≤2 TeV , the absolute values of the relative correction parameter are larger than 5%. We calculate the forward-backward asymmetries and left-right asymmetries for the process e^＋e^-→c^＋c^-, with both the universal and anomaly-free fermion embeddings. Bounds on Z＇ masses are also estimated within 95% confidence level.
