Measurement of Bd mixing using opposite-side flavor tagging

TL;DR

This paper measures the $B^0_d$ mixing frequency and calibrates an opposite-side flavor tagger using data from the DØ experiment, achieving a tagging power of about 2.5% and confirming known mixing parameters.

Contribution

It introduces a new combined likelihood-ratio method for flavor tagging and calibrates its performance with real collider data.

Findings

Effective tagging power of 2.48% was achieved.

Measured $B^0_d$ mixing frequency agrees with the world average.

The method improves flavor tagging in $B$ meson studies.

Abstract

We report on a measurement of the $B^0_d$ mixing frequency and the calibration of an opposite-side flavor tagger in the D{\O}experiment. Various properties associated with the $b$ quark on the opposite side of the reconstructed $B$ meson were combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance was tested with data, using a large sample of reconstructed semileptonic $B \to \mu \dzero X$ and $B \to \mu \dst X$ decays, corresponding to an integrated luminosity of approximately 1 fb$^{-1}$. The events were divided into groups depending on the value of the combined tagging variable, and an independent analysis was performed in each group. Combining the results of these analyses, the overall effective tagging power was found to be eD^2 = (2.48 \pm 0.21 (stat.) ^{+0.08}_{-0.06} (syst.))%. The measured $B^0_d$ mixing frequency dmd = 0.506 \pm 0.020 {\rm (stat) \pm 0.016 (syst) ps}^{-1} is in good agreement with the world average value.