# Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV

## TL;DR

This study introduces a data-driven method to measure jet broadening in heavy-ion collisions by subtracting flow backgrounds, revealing increased jet widths in central Au+Au collisions at 200 GeV.

## Contribution

A novel background subtraction technique using pseudorapidity gaps enables precise measurement of jet shape broadening in heavy-ion collisions.

## Key findings

- Jet widths increase with collision centrality.
- Correlation shapes are consistent with Gaussian distributions.
- Evidence of jet broadening in the quark-gluon plasma created in central collisions.

## Abstract

High transverse momentum ($p_T$) particle production is suppressed due to parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest $p_T$ has been elusive to measure because of large anisotropic backgrounds. We report a data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV with the STAR experiment. The correlation shapes, for trigger particle $p_T>3$ GeV/$c$ and various associated particle $p_T$ ranges within $0.5<p_T<10$ GeV/$c$, are consistent with Gaussians and their widths are found to increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.