Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector

TL;DR

This paper reports the most precise measurement to date of the semileptonic charge asymmetry in B0 meson mixing, using data from the D0 detector at Fermilab, which helps test the Standard Model and search for new physics.

Contribution

It provides a novel, highly precise measurement of the B0 meson semileptonic charge asymmetry using two decay channels and data-driven correction methods, improving upon previous results.

Findings

Measured a^d_{sl} = [0.68 ± 0.45 (stat.) ± 0.14 (syst.)]%

Achieved the most precise single measurement of this parameter

Results are consistent with Standard Model predictions

Abstract

We present a measurement of the semileptonic mixing asymmetry for B0 mesons, a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- -> K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1} of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at the Fermilab Tevatron collider. We extract the charge asymmetries in these two channels as a function of the visible proper decay length (VPDL) of the B0 meson, correct for detector-related asymmetries using data-driven methods, and account for dilution from charge-symmetric processes using Monte Carlo simulation. The final measurement combines four signal VPDL regions for each channel, yielding a^d_{sl} = [0.68 \pm 0.45 \text{(stat.)} \pm 0.14 \text{(syst.)}]%. This is the single most precise measurement of this parameter, with uncertainties smaller than the current world average of B factory measurements.