Measurement of the branching ratios of the Z0 into heavy quarks

Le résumé fourni par la source

We measure the hadronic branching ratios of the ${Z}^{0}$ boson into heavy quarks: ${R}_{b}={\ensuremath{\Gamma}}_{{Z}^{0}\ensuremath{\rightarrow}b\overline{b}}/{\ensuremath{\Gamma}}_{{Z}^{0}\ensuremath{\rightarrow}\mathrm{hadrons}}$ and ${R}_{c}={\ensuremath{\Gamma}}_{{Z}^{0}\ensuremath{\rightarrow}c\overline{c}}/{\ensuremath{\Gamma}}_{{Z}^{0}\ensuremath{\rightarrow}\mathrm{hadrons}}$ using a multitag technique. The measurement was performed using about 400 000 hadronic ${Z}^{0}$ events recorded in the SLC Large Detector experiment at SLAC between 1996 and 1998. The small and stable SLAC Linear Collider beam spot and the CCD-based vertex detector were used to reconstruct bottom and charm hadron decay vertices with high efficiency and purity, which enables us to measure most efficiencies from data. We obtain, ${R}_{b}=0.21604\ifmmode\pm\else\textpm\fi{}0.00098(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.00073(\mathrm{syst}.)\ensuremath{\mp}0.00012({R}_{c})$ and, ${R}_{c}=0.1744\ifmmode\pm\else\textpm\fi{}0.0031(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.0020(\mathrm{syst}.)\ensuremath{\mp}0.0006({R}_{b})$.

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