$B_s \rightarrow J/\psi\phi$ RUN-1 results and studies of $B^\pm$ mass with RUN-2 data at ATLAS

We present a flavour tagged time dependent angular analysis of the $B_s \rightarrow J/\psi\phi$ decay, using 14.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector from 8 TeV LHC proton-proton collisions recorded in 2012. $CP$-violation in this channel is described by a weak phase $\phi_s$, which is sensitive to new physics contributions. Measured parameters are statistically combined with those from 4.9 fb$^{-1}$ of 7 TeV data, leading to the final results from ATLAS in RUN 1: $\phi_s = -0.098 \pm 0.084 \mathrm{(stat.)} \pm 0.040 \mathrm{(syst.) rad}$, which is in good agreement with Standard Model expectations. Also other measured parameters are consistent with the world average. The performance of the ATLAS detector in reconstructing $B^\pm \rightarrow J/\psi K^\pm$ candidates is also presented, using 3.2 fb$^{-1}$ of integrated luminosity of 13 TeV LHC proton-proton collisions. The $B^\pm$ mass is used to validate the momentum calibration of the Inner Detector tracking at low-to-medium $p_\mathrm{T}$ values with 2015 data.