Recent Heavy-Flavor Measurements from OPAL

TL;DR

This paper presents recent heavy-flavor measurements from OPAL using LEP1 data, including polarization of b baryons, limits on excited D*' production, and branching ratios of Lambda_b decays, providing insights into b-hadron properties.

Contribution

It reports new measurements of b baryon polarization, sets upper limits on D*' production, and updates Lambda_b decay branching ratios, enhancing understanding of heavy-flavor physics.

Findings

Measured b baryon polarization to be -0.56^{+0.20}_{-0.13}

Set 95% CL upper limit on D*' production at 2.1x10^{-3}

Calculated Lambda_b decay branching ratios and their ratios

Abstract

A selection of recent heavy-flavor results from OPAL using the LEP1 data sample are presented. The average polarization of b baryons in hadronic Z^0 decay has been measured to be -0.56^{+0.20}_{-0.13} (stat.) +- 0.09(syst.) using semileptonic decays of Lambda_b baryons. A search has been conducted for the radially excited D*' and has produced a 95% CL upper limit on its production of f(Z^0 -> D*'+-(2629))xBr(D*'+- -> D*+- pi+ pi-) < 2.1x10^{-3}. Finally, the measurement of the product branching ratio $f(b -> Lambda_b)xBr(Lambda_b -> Lambda X)= (2.67 +- 0.38 (stat) ^{+0.67}_{-0.60}(syst.))% has been made. This measurement, along with an earlier measurement of the product branching ratio f(b -> Lambda_b)xBr(Lambda_b -> Lambda l X), has been used to compute an updated R_{Lambda l} = Br(Lambda_b -> Lambda l X)/Br(Lambda_b -> \Lambda X)= (8.0 +- 1.2 (stat.) +- 0.9 (syst.))%, consistent with the expected low semileptonic branching fraction of the Lambda_b inferred from its short lifetime compared to the other b hadrons.