$\Delta\eta$-$\Delta\phi$ correlations and the ridge structure in STAR

TL;DR

This study investigates the evolution of di-hadron correlations in central Au+Au collisions at 200 GeV, revealing a ridge structure linked to initial state fluctuations and comparing results with p+p data.

Contribution

It introduces a comprehensive analysis of the $\Delta\eta$-$\Delta\phi$ correlation evolution, incorporating higher harmonic components and modeling initial state fluctuations.

Findings

Observation of a smooth evolution of correlation structures with increasing $p_T$

Reproduction of the ridge structure near $\langle p_T \rangle$ = 2.7 GeV/c

Comparison of extracted parameters with model predictions and p+p data

Abstract

Triggered di-hadron correlation studies using central Au+Au collisions at $\sqrt{S_{NN}}$ = 200 GeV in STAR revealed a novel ridge-like structure in two dimensions ($\Delta\eta$,$\Delta\phi$) for high $p_{T}$ particles. A similar structure is also present in an inclusive un-triggered di-hadron correlation analysis. We study the <$p_{T}$> evolution of di-hadron correlations by increasing the lower $p_{T}$ acceptance of both charged particles. A smooth evolution of data is observed and our results reproduce the triggered analysis structure near <p_{T}> = 2.7 GeV/c. We quantify the correlation structure evolution by fitting a model function. The model function emphasizes possible initial state fluctuation contributions via the use of higher harmonic model components $v_{n}$ (n=1,2,3,4,5) and a remainder which is modeled via an asymmetric 2d Gaussian. The extracted parameters are compared to model predictions and p+p data at $\sqrt{S_{NN}}$ = 200 GeV and possible origins of the nearside structure are discussed.