Measurement of the relative width difference of the B-0-(B)over-bar(0) system with the ATLAS detector

Abstract

This paper presents the measurement of the relative width difference ∆Γd/Γd of the B0- ¯ B0 system using the data collected by the ATLAS experiment at the LHC in pp collisions at √s = 7TeV and √s = 8TeV 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.