Measurement of the Relative Width Difference of the B0-B0 System With the ATLAS Detector

Abstract

Abstract: This paper presents the measurement of the relative width difference ∆Γd/Γd 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 25.2fb−1. The value of ∆Γd/Γd is obtained by comparing the decay-time distributions of B0 → J/ψKS and B0 → J/ψK∗0(892) decays. The result is ∆Γd/Γd = (−0.1±1.1 (stat.)± 0.9 (syst.)) × 10−2. Currently, this is the most precise single measurement of ∆Γd/Γd. It agrees with the Standard Model prediction and the measurements by other experiments.