Search

The production of Bcand B*cmesons at a Z-factory (an e+e-collider operating at energies around the Zpole) is calculated up to the next-to-leading order (NLO) QCD accuracy. The results show that the dependence of the total cross sections on the renormalization scale μ is suppressed by the corrections, and the NLO corrections enhance the total cross sections of Bcby 52% and of B*cby 33% when the renormalization scale is taken at μ= 2mb. To observe the various behaviors of the production of the mesons Bcand B*c, such as the differential cross section vs. the out-going angle, the forward-backward asymmetry, and the distribution vs. the energy fraction zup to NLO QCD accuracy as well as the relevant K-factor (NLO to LO) for the production, are calculated, and it is pointed out that some of the observables obtained in the present work may be used as a specific precision test of the standard model.

Abstract: We analyze the cross section of e + e − → τ +µ− within the frameworks of SM and its Z′ extension. The theoretical prediction of the SM on the total cross section is suppressed by the tiny neutrino masses. On the other hand, the contributions from Z′ to the cross section are enhanced drastically because of the tree level FCNC couplings among Z′ and leptons.