Professor Daniela Bortoletto

Abstract:

A measurement of the B0$$B^{0}$$ meson lifetime using B0→J/ψK∗0$$ B^{0} \rightarrow J/\psi K^{*0} $$ decays in data from 13 TeV$$\text {TeV}$$ proton–proton collisions with an integrated luminosity of 140fb-1$$ 140~\mathrm {fb^{-1}} $$ recorded by the ATLAS detector at the LHC is presented. The measured effective lifetime is τ=1.5053±0.0012(stat.)±0.0035(syst.)ps.$$ \tau = 1.5053\pm 0.0012~\mathrm {(stat.)} \pm 0.0035~\mathrm {(syst.)~ps}. $$The average decay width extracted from the effective lifetime, using parameters from external sources, is Γd=0.6639±0.0005(stat.)±0.0016(syst.)±0.0038(ext.)ps-1,$$\begin{aligned} \Gamma _d = 0.6639\pm 0.0005~\mathrm {(stat.)} \pm 0.0016~\mathrm {(syst.)}\\ \pm 0.0038~\text {(ext.)} \text {~ps}^{-1}, \end{aligned}$$where the uncertainties are statistical, systematic and from external sources. The earlier ATLAS measurement of Γs$$\Gamma _s$$ in the Bs0→J/ψϕ$$B^{0}_{s} \rightarrow J/\psi \phi $$ decay was used to derive a value for the ratio of the average decay widths Γd$$\Gamma _d$$ and Γs$$\Gamma _s$$ for B0$$B^{0} $$ and Bs0$$B^{0}_{s} $$ mesons respectively, of ΓdΓs=0.9905±0.0022(stat.)±0.0036(syst.)±0.0057(ext.).$$ \frac{\Gamma _d }{\Gamma _s } = 0.9905\pm 0.0022~\text {(stat.)} \pm 0.0036~\text {(syst.)} \pm 0.0057~\text {(ext.)}. $$The measured lifetime, average decay width and decay width ratio are in agreement with theoretical predictions and with measurements by other experiments. This measurement provides the most precise result of the effective lifetime of the B0$$B^{0}$$ meson to date.