Feasibility study on extracting the gluon polarization in Di-Jet production in polarized pp collisions at RHIC

Abstract

The STAR experiment at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is carrying out a spin physics program at is = 200 - 500 GeV to gain a deeper insight into the spin structure and dynamics of the proton. These studies provide fundamental tests of Quantum Chromodynamics (QCD). One of the main objectives of the STAR spin physics program is the determination of the polarized gluon distribution function through a measurement of the longitudinal double-spin asymmetry, ALL, for various processes. Di-Jet production is of particular interest since it allows a direct access of the underlying partonic kinematics, in particular the reconstruction of the gluon momentum fraction relative to the respective proton momentum. The main objective of this study is to examine to what extent the gluon polarization can be measured as a function of the gluon momentum fraction in leading-order perturbation theory. We propose a leading order method to extract the gluon polarization from ALL, and find that it transforms the problem into simply solving the quadratic formula.