  In the (Delta phi)-(Delta eta) correlation associated with a near-side jet
observed by the STAR Collaboration in heavy-ion collisions at RHIC [Ref. 1-6],
the ridge structure can be explained by the momentum kick model in which the
ridge particles are identified as medium partons which suffer a collision with
the jet and acquire a momentum kick along the jet direction. If this is indeed
the correct mechanism, the ridge structure associated with the near-side jet
may be used to probe the parton momentum distribution at the moment of the
jet-parton collision, leading to the result that at that instant the parton
temperature is slightly higher and the rapidity width substantially greater
than corresponding quantities of their evolution product inclusive particles at
the end point of the nucleus-nucleus collision.
