$B$-meson decays into charmonium states in the ATLAS experiment

The paper presents several recent ATLAS results on the analyses of B-meson decays into charmonium states. These include the measurements of B$^{+}$ mass and the fractions of J/ψ mesons produced in b-hadron decays in pp collisions at $\sqrt s$ = 13 TeV in the center of mass system. The measured partial widths and polarizations in B$_{c}^{+}$ → J/ψD$_{s}^{(*)+}$ decays and CP-violation parameters in B$_{s}^{0}$ → J/ψϕ decays in pp collisions at 7 and 8 TeV in the center of mass system are also presented.