QCD evolution with longitudinal fields and heavy quarks
  QCD evolution equations that naturally include longitudinal (non-propagating) fields and heavy quarks are derived. We start with the integral equations of quantum field kinetics and obtain the master equations, similar to DGLAP evolution equations after several consecutive approximations. We demonstrate that in their primary form, the evolution equations include a new element, feed-back via longitudinal fields, leading to a low-x enhancement in the e-p DIS cross section. We show that the structure function F_L is very sensitive to the dynamics of the longitudinal fields and that the heavy quarks in evolution equations make this effect even more pronounced. 
A.Makhlin and E. Surdutovich