I know that for some observables in QCD, e.g. inclusive DIS cross sections, one can use factorisation by writing said observable as a convolution of hard scattering coefficients with PDFs. But what is mass factorisation in particular and how does it differ from the factorisation above? Are there other types of factorisation? Can they all be recast in the framework of dimensional regularisation of IR-divergences? Example calculations are very welcome!