Exploring early parton momentum distribution with the ridge from the near-side jet

In a central nucleus-nucleus collision at high energies, medium partons kicked by a near-side jet acquire a momentum along the jet direction and subsequently materialize as the observed ridge particles. They carry direct information on the early parton momentum distribution which can be extracted by using the ridge data for central AuAu collisions at root(NN)-N-S = 200 GeV. The extracted parton momentum distribution has a thermal- like transverse momentum distribution but a non- Gaussian, relatively flat rapidity distribution at mid-rapidity with sharp kinematic boundaries at large rapidities that depend on the transverse momentum.