Phase diagram of QCD in a magnetic background

We provide numerical evidence that the thermal QCD crossover turns into a first order transition in the presence of large enough magnetic background fields. The critical end point is found to be located between eB 4 GeV 2 [where the pseudocritical temperature is T c 98 AE 3 MeV] and eB 9 GeV 2 [where the critical temperature is T c 63 AE 5 MeV]. Results are based on the analysis of quark condensates and number susceptibilities, determined by lattice simulations of N f 2 1 QCD at the physical point, discretized via rooted stout staggered fermions and a Symanzik tree level improved pure gauge action, adopting two different lattice spacings, a 0.114 and 0.086 fm, for eB 9 GeV 2 and three, a 0.114, 0.086, and 0.057 fm, for eB 4 GeV 2 . We also present preliminary results regarding the confining properties of the thermal theory, suggesting that they could change drastically going across the phase transition.