Measurement of the relative width difference of the $$ {B}^0\hbox{-} {\overline{B}}^0 $$ system with the ATLAS detector

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 25.2 fb−1. The value of ∆Γd/Γd is obtained by comparing the decay-time distributions of B 0 → J/ψKS and B 0 → 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.