Precision measurement of the $B^{0}$ meson lifetime using $B^{0} \rightarrow J/\psi K^{*0}$ decays with the ATLAS detector

TL;DR

This paper reports the most precise measurement to date of the $B^{0}$ meson lifetime using $B^{0} o J/psi K^{*0}$ decays from ATLAS data at 13 TeV, confirming theoretical predictions and previous experimental results.

Contribution

It presents the most precise measurement of the $B^{0}$ meson lifetime and decay widths using ATLAS data, improving accuracy over prior measurements.

Findings

Effective lifetime measured as 1.5053 ps with small uncertainties.

Average decay width $ au$ and decay width ratio $rac{ au_d}{ au_s}$ are consistent with predictions.

Results agree with previous measurements and theoretical models.

Abstract

A measurement of the $B^0$ meson lifetime using $B^0 \to J/\psi K^{*0}$ decays in data from 13 TeV proton-proton collisions with an integrated luminosity of 140 fb$^{-1}$ recorded by the ATLAS detector at the LHC is presented. The measured effective lifetime is $$ \tau = 1.5053 \pm 0.0012 ~\mathrm{(stat.)} \pm 0.0035 ~\mathrm{(syst.)~ps}. $$ The average decay width, extracted from the effective lifetime and using a parameter from external sources, is $$ \Gamma_d = 0.6643 \pm 0.0005 ~\mathrm{(stat.)} \pm 0.0016 ~\mathrm{(syst.)}~\mathrm{ps}^{-1}, $$ where the uncertainties are statistical and systematic. The uncertainty due to external sources is negligible at the given precision. The earlier ATLAS measurement of $\Gamma_s$ in the $B^0_s \to J/\psi\phi$ decay was used to derive a value for the ratio of the average decay widths $\Gamma_d$ and $\Gamma_s$ for $B^0$ and $B^0_s$ mesons respectively, of $$ \frac{\Gamma_d}{\Gamma_s} = 0.9910 \pm 0.0022 ~\mathrm{(stat.)} \pm 0.0036 ~\mathrm{(syst.)}. $$ The measured lifetime, average decay width and decay width ratio are in agreement with theoretical predictions and with measurements by other experiments. This measurement provides the most precise result of the effective lifetime of the $B^0$ meson to date.