Measurement of the relative width difference of the B⁰‐B¯⁰ system with the ATLAS detector

Abstract

This paper presents the measurement of the relative width difference ΔΓ_d/Γ_d of the B⁰‐B¯⁰ system using the data collected by the ATLAS experiment at the LHC in pp collisions at √s = 7 TeV and √s = 8 TeV and corresponding to an integrated luminosity of 25.2 fb^-1. The value of ΔΓ_d/Γ_d is obtained by comparing the decay-time distributions of B⁰ → J/ψK_S and B⁰ → J/ψK*⁰(892) decays. The result is ΔΓ_d/Γ_d = (−0.1±1.1 (stat.)± 0.9 (syst.)) × 10^-2. Currently, this is the most precise single measurement of ΔΓ_d/Γ_d. It agrees with the Standard Model prediction and the measurements by other experiments.