Chiral properties of strong interactions in a magnetic background

We investigate the chiral properties of QCD in the presence of a magnetic background field and in the low temperature regime, by lattice numerical simulations of N-f = QCD. We adopt a standard staggered discretization, with a pion mass around 200 MeV, and explore a range of magnetic fields (180 MeV)(2) <= vertical bar e vertical bar B <= (700 MeV)(2), in which we study magnetic catalysis, i.e. the increase of chiral symmetry breaking induced by the background field. We determine the dependence of the chiral condensate on the external field, compare our results with existing model predictions and show that a substantial contribution to magnetic catalysis comes from the modified distribution of non-Abelian gauge fields, induced by the magnetic field via dynamical quark loop effects.