We study the medium modified fragmentation function in high-energy heavy-ion collisions. We show that the ACSX and QW formalisms are equivalent to each other in the high-Q2 limit in both theoretical and numerical aspects.
We study the effect of gluon number fluctuations （Pomeron loops） on the proton structure function at HERA. It is shown that the description of charm and bottom quarks and longitudinal structure functions are improved, with x^2/d.o.f=0.803 （fluctuations） as compared with x^2/d.o.f=0.908 （without fluctuations）, once the gluon number fluctuations are included. We find that in the gluon number fluctuation case the heavy quarks do not play an important role in the proton structure function as the saturation model. The successful description of the HERA data indicates that the gluon number fluctuation could be one of the key mechanisms to describe the proton structure function at HERA energies.
