In order to understand more precisely the gluon saturation phenomenon at low x and the kinematical range in which it happens, higher order corrections need to be included. With that goal in mind, the NLO corrections to DIS structure functions in the dipole factorization and to various particle production processes at the LHC have been recently calculated, as well as the BK and JIMWLK evolutions at NLL accuracy. These calculations are often done in light-front perturbation theory, which simplifies the inclusion of gluon saturation effects. So far, for simplicity, almost all of these calculations have been restricted to the case of massless quarks. However, the charm and bottom quarks are known to give a sizable contribution to DIS at HERA, and should thus be considered.
The main new issue arising in the NLO calculations with massive quarks is the quark mass renormalization. Indeed, there was a longstanding confusion in the literature about mass renormalization in gauge theories in light-front perturbation theory, leading to inconsistent results. I will present how mass renormalization can be properly done for QCD and QED in light-front perturbation theory, by using a Lorentz-invariant UV regularization procedure.