6533b86efe1ef96bd12cbd84

RESEARCH PRODUCT

Lifetime and production rate of beauty baryons from Z decays

subject

description

The production and decay of beauty baryons (b-baryons) have been studied using 1.7 \times 10^6 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a \Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed \Lambda_c baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: \begin{eqnarray*} f(\qb \ra \Bb) \times \BR(\Bb \ra \mLs \ell\bar{\nu}_{\ell}\X) & = & (0.30 \pm 0.06 \pm0.04)\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \mLc \ell\bar{\nu}_{\ell}\X) & = & (1.18 \pm 0.26^{+0.31}_{-0.21})\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \prot\mu\bar{\nu}_{\mu}\X) & = & (0.49\pm0.11\pm^{+0.15}_{ -0.11})\% . \end{eqnarray*} The average b-baryon lifetime was determined to be:\par \vspace{0.4cm} \centerline {\tau = 1.21 ^{+.21}_{-.18}(stat.)\pm0.04(exp.syst.) ^{+.02}_{-.07}(th.syst.) ps.}