Multiple Parton Scattering In Nuclei: Modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (Dglap) Evolution For Fragmentation Functions

Within the framework of generalized factorization of higher-twist contributions to semi-inclusive cross sections of deeply inelastic scattering (DIS) off a large nucleus, multiple parton scattering leads to an effective medium-modified fragmentation function and the corresponding medium-modified DGLAP evolution equations. We extend the study to include gluon multiple scattering and induced quark-antiquark production via gluon fusion. We numerically solve these medium-modified DGLAP (mDGLAP) evolution equations and study the scale (Q(2)), energy (E), length (L), and jet transport parameter ((q) over cap) dependence of the modified fragmentation functions for a jet propagating in a uniform medium with finite length (a "brick" problem). We also discuss the concept of parton energy loss within such mDGLAP evolution equations and its connection to the modified fragmentation functions. With a realistic Wood-Saxon nuclear geometry, we calculate the modified fragmentation functions and compare them to experimental data on DIS off large nuclei. The extracted jet transport parameter at the center of a large nucleus is found to be (q) over cap (0) = 0.024 +/- 0.008 GeV2/fm.