# Quark Matter 2012

12-18 August 2012
US/Eastern timezone

## Forward azimuthal correlations in 200 GeV p+p and d+Au collisions at STAR

15 Aug 2012, 12:20
20m
Empire ()

### Empire

Oral Presentation Pre-equilibrium and initial state dynamics

### Speaker

Xuan Li (Shandong University)

### Description

The proton gluon distribution function increases rapidly with decreasing x at fixed $Q^{2}$, but cannot increase indefinitely as x goes to 0. Gluon saturation is expected at a low x value when gluon recombination balances gluon splitting. The nuclear (with atomic mass number A) gluon distribution is approximately $A^{1/3}$ larger than the nucleon gluon distribution function at the same x [1]. STAR is sensitive to x between 0.001 and 0.02 for the nuclear gluon distribution via di-jet measurements with calorimeter subsystems covering -1 < eta < 4. The STAR collaboration has measured forward $\pi{0}$-$\pi{0}$ correlations and forward+mid-rapidity correlations in p+p and d+Au collisions at $\sqrt{s}=200GeV$. The suppression of the away-side peak observed in forward-forward correlations in central d+Au collisions is consistent with the CGC expectation [2,3]. Such suppression does not appear in the forward+mid-rapidity correlations. The Endcap Electromagnetic Calorimeter (EEMC) at STAR covers pseudo-rapidity between 1.08 and 2, providing the opportunity to probe gluons at intermediate x via forward+near-forward correlations. Azimuthal correlations between $\pi{0}$ in the Forward Meson Spectrometer (FMS) and jet-like clusters in the EEMC are sensitive to the nuclear gluon distribution in 0.003

### Primary author

Xuan Li (Shandong University)

 Slides

Paper files: