  In strong magnetic fields, massless electrons in graphene populate
relativistic Landau levels with the square-root dependence of each level energy
on its number and magnetic field. Interaction-induced deviations from this
single-particle picture were observed in recent experiments on cyclotron
resonance and magneto-Raman scattering. Previous attempts to calculate such
deviations theoretically using the unscreened Coulomb interaction resulted in
overestimated many-body effects. This work presents many-body calculations of
cyclotron and magneto-Raman transitions in single-layer graphene in the
presence of Coulomb interaction, which is statically screened in the
random-phase approximation. We take into account self-energy and excitonic
effects as well as Landau level mixing, and achieve good agreement of our
results with the experimental data for graphene on different substrates.
Important role of a self-consistent treatment of the screening is found.
