ATLAS results on charmonium production and $B_c$ production and decays

Recent results from the ATLAS experiment at the LHC on the charmonium production and on the $B_c$ production and decays are presented. These include studies of the associated production of the $J/\psi$ meson and $W$ boson, the measurement of $J/\psi$ and $\psi(\mathrm{2S})$ mesons differential production cross-sections, the measurement of the differential ratios of the $B_c^+$ and $B^+$ production cross-sections, and the new results on the $B_c^+$ decays to $J/\psi D_s^{(*)}$ final states. The results are obtained with $pp$ collision data collected at centre-of-mass energies $\sqrt{s} = 8$ and 13 TeV.