Initial conditions for the modified evolution of fragmentation functions in the nuclear medium

Initial conditions are required to solve medium modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (mDGLAP) evolution equations for modified fragmentation functions due to multiple scatterings and parton energy loss. Such initial conditions should in principle include energy loss for partons at scale Q₀ above which mDGLAP evolution equations can be applied. Several models for the initial condition motivated by induced gluon bremsstrahlung in perturbative QCD are used to calculate the modified fragmentation functions in nuclear medium and to extract the jet transport parameter q̂ from fits to experimental data in deeply inelastic scattering (DIS) off nuclei. The model with a Poisson convolution of multiple gluon emissions is found to provide the overall best χ²/d.o.f. fit to the HERMES data and gives a value of q̂0≈0.020±0.005 GeV²/fm at the center of a large nucleus.