Simultaneous Measurement of the B0 Meson Lifetime and Mixing Frequency with B0 --> D*- l+ nu_l Decays

TL;DR

This paper reports a precise measurement of the B0 meson lifetime and its oscillation frequency using a large dataset of B0 decay events, employing a simultaneous fit approach at the BABAR experiment.

Contribution

It introduces a simultaneous measurement method for B0 lifetime and mixing frequency using unbinned maximum-likelihood fit on a large dataset, improving precision over previous measurements.

Findings

B0 lifetime measured as approximately 1.523 ps

B0 oscillation frequency measured as approximately 0.492 ps^-1

Results are consistent with Standard Model predictions

Abstract

We measure the B0 lifetime tau_B0 and the B-Bbar oscillation frequency Deltam_d with a sample of approximately 14,000 exclusively reconstructed B0 -> D*- l+ nu_l signal events, selected from 23 million B-Bbar pairs recorded at the Upsilon(4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The b-quark flavor of the other B at the time of decay and its decay position are determined inclusively. The lifetime and oscillation frequency are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in B decay times (Delta-t), the calculated uncertainty on Delta-t, the signal and background probabilities, and b-quark tagging information for the other B. The preliminary results are tau_B0 = (1.523 +0.024 -0.023 (stat) +/- 0.022 (syst)) ps and Deltam_d = (0.492 +/- 0.018 (stat) +/- 0.013 (syst)) ps^-1. The statistical correlation coefficient between tau_B0 and Deltam_d is -0.22.