A study of charm quark production in beauty quark decays with the OPAL detector at LEP.

摘要

The production of charm quarks in beauty quark decays has been studied with the OPAL detector at the Large Electron Positron collider near Geneva, Switzerland. The branching ratio Br(b → DD¯X) has been measured using hadronic Z0 decays collected between 1993 and 1995. Here b refers to the admixture of weakly decaying hadrons containing a b quark that are produced in electron-positron annihilations at a centre of mass energy equal to the mass of the Z0 boson. The impact parameter significance of tracks in tagged b-jets is used to differentiate b → DD¯X decays from other decays. The result is Brb→D D&d1;X=&parl0;10.0± 3.2stat. +2.4-2.9syst. det. +10.4-9.0syst. phys.&parr0; %. where syst. det. is the systematic uncertainty due to the modelling of the detector, and syst. phys. is the systematic uncertainty due to the modelling of the underlying particle physics. Using this result, the average number of charm and anti-charm quarks produced in a beauty quark decay, n_c, is found to be $1.12+0.11-0.10$.