Precision measurement of the B0 meson lifetime using B0 → J/ψ K∗0 decays with the ATLAS detector

Abstract

A measurement of the B0 meson lifetime usingB0 RIGHTWARDS ARROW J/ψKASTERISK OPERATOR0 decays in data from 13 TeV proton-protoncollisions with an integrated luminosity of 140 fb-1 recordedby the ATLAS detector at the LHC is presented. The measuredeffective lifetime isτ = 1.5053 +- 0.0012 (stat.) +- 0.0035 (syst.) ps.The average decay width extracted from the effective lifetime,using parameters from external sources, isd = 0.6639 +- 0.0005 (stat.) +- 0.0016 (syst.)+-0.0038 (ext.) ps-1,where the uncertainties are statistical, systematic and fromexternal sources. The earlier ATLAS measurement of s inthe B0sRIGHTWARDS ARROW J/ψφ decay was used to derive a value for theratio of the average decay widths d and s for B0 and B0smesons respectively, ofds= 0.9905+-0.0022 (stat.)+-0.0036 (syst.)+-0.0057 (ext.).Themeasured lifetime, average decay width and decay widthratio are in agreement with theoretical predictions and withmeasurements by other experiments. This measurement providesthe most precise result of the effective lifetime of the B0 meson to date.