The B_c Meson Production At The High Luminosity E~+e~-Collider

The production of B_cmeson and its excited states is studied within the framework ofNon-Relativistic Quantum Chromodynamics （NRQCD） in the high luminositye⁺e^-collider （such as super Z-factory）. Because of the Z0-boson resonance, theproduction of B_cmeson could be greatly enhanced when the collision energy is set to bearound the Z0-boson resonance. Thus such a e⁺e^-collider shall provide a usefulplatform to study the properties of B_cmeson.Recently, a e⁺e^-collider called super Z-factory running around the Z0-bosonresonance is proposed to be constructed in China by a Chinese group with highluminosity10³⁴¹0³⁶cm^-2s^-1. Considering the experimental condition, we detailedlystudied the production of B_cmeson through e⁺e^-annihilation,e⁺e^-â†'γ*/Z₀|（cb）â†'γb c, in present thesis under the NRQCD framework, wherethe （c b）-quarkonium could be in color-singlet S-wave states, color-singlet P-wavestates or color-octet S-wave states. While all the excited states could decay to theground state with100%efficiency via electromagnetic interactions. According to theNRQCD factorization formulas, the cross section could be factorized to two parts: theshort distance one computed in perturbative theory and expressed as the cross section ofthe hard processe⁺e^-â†'γ*/Z₀c b b c; the non-perturbative but universal longdistance one, related to the transition from the quarks c bto the observablequarkonium state of the B_cmeson. The non-perturbative long distance matrix elementusually determined by experiment data, but here fortunately color-singlet matrixelement could be related to the wave function at the origin or its first derivative andfinally be determined by potential model. With regard to the hard process amplitude, itwould be much simple to adopt the improved amplitude trace approach to get theanalytic result at the amplitude level. That is a great improvement compared with thetraditional amplitude square trace method, which is difficult to obtain the analytic resultbecause of considering the effect of quark mass. Specially, as the main part, we presentthe calculation of the production of B_cmeson through Z0-boson decay in the improvedamplitude trace approach.In addition to the calculation of cross section and decay width, we also study theuncertainties of cross section and the differential cross section caused by theuncertainties of b-quark and c-quark masses. And the cross section deviation when the center-of-mass energy deviate slightly from Z0resonance peak is also discussed. Theresult shows that the super-Z factory will accumulate about104¹06B_cevents a year atthe planned experimental condition. That will truly make the super-Z factory anexperiment platform for the study of double heavy B_cmeson as a complement of theLarge Hadron Collider at CERN.Meanwhile, we write a generator for stimulating the production of B_cmeson ine⁺e^-collider based on the previous calculation. The Monte Carlo generator namedBEEC is written following the formate of PYTHIA and can be treated as externalprocess of PYTHIA, thus the subroutines in PYTHIA could be used conveniently. Theevent generator could choose VEGAS for high dimensional phase space integration andRAMBOS to generate the requested event points. Several mechanisms wereprogrammed in the generator, such as the hit-and-miss technique used to unweight thegenerated events. Eventually BEEC could get the efficient simulation by cooperatingwith PYTHIA to do the further hadronization.