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

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