$B$-hadrons spectroscopy and decay properties with the ATLAS experiment

The parity violating asymmetry parameter $\alpha_b$ in $\Lambda_b \rightarrow \Lambda J/\psi$ decay was measured using the ATLAS detector in proton-proton collisions at the Large Hadron Collider at $\sqrt{s} = 7$~TeV, using data collected in the 2011 run. Furthermore, a search for excited states of the $B_c^\pm$ meson was performed using 4.9~f\invb of 7 TeV and 19.2~f\invb of 8 TeV proton-proton collision data. A new state was observed through its hadronic transition to the ground state, with an invariant mass of 6842~$\pm$~7~$\pm$~4~MeV, consistent with predictions for the $B_c^\pm(2S)$ meson.