Measurement of the semileptonic b branching fractions and average b mixing parameter in Z decays

Abstract

Abstract.

The semileptonic branching fractions for primary and cascade b decays \({\mathrm{BR}}(b\rightarrow \ell^-)\), \(\mathrm{BR}(b\rightarrow c\rightarrow \ell^+)\) and \(\mathrm{BR}(b\rightarrow\bar c\rightarrow \ell^-\) were measured in hadronic Z decays collected by the DELPHI experiment at LEP. The sample was enriched in b decays using the lifetime information and various techniques were used to separate leptons from direct or cascade b decays. By fitting the momentum spectra of di-leptons in opposite jets, the average b mixing parameter \(\bar{\chi}\) was also extracted. The following results have been obtained: