Exploring Early Parton Momentum Distribution with the Ridge from the Near-Side Jet

TL;DR

This paper investigates how the ridge phenomenon in high-energy nucleus-nucleus collisions reveals the early momentum distribution of partons, showing a thermal-like transverse profile and a flat rapidity distribution with kinematic limits.

Contribution

It introduces a method to extract the early parton momentum distribution from ridge data in central AuAu collisions at 200 GeV.

Findings

Parton momentum distribution is thermal-like transversely.

Rapidity distribution is flat at mid-rapidity with sharp boundaries.

Distribution depends on transverse momentum.

Abstract

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 \sqrt{s_{NN}}=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.