22-27 September 2016
East Lake International Conference Center
Asia/Chongqing timezone
<a href="http://hp2016.ccnu.edu.cn">http://hp2016.ccnu.edu.cn</a>

Characterizing the away-side jet with robust flow background subtraction via two-particle and three-particle correlations in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV in STAR

25 Sep 2016, 09:30
20m
Shi-Yan Hall (East Lake International Conference Center)

Shi-Yan Hall

East Lake International Conference Center

Donghu Road 142, Wuchang District, Wuhan, Hubei, China

Speaker

Kun Jiang (University of Science and Technology of China)

Description

Jets are modified in relativistic heavy-ion collisions due to jet-medium interactions. Measurements of jet medium modifications have so far been obscure because of the large underlying anisotropic flow background. In this analysis we devise a novel method to subtract the flow background using data. We select events with a large recoil momentum ($P_x$) within a pseudorapidity ($\eta$) window of $0.5<|\eta|<1$ from a high-$p_T$ trigger particle to enhance the away-side jet population. Di-hadron azimuthal correlations are analyzed with associated particles in two $\eta$ ranges ($−0.5<\eta<0$ and $0<\eta<0.5$) symmetric about midrapidity, one (“close-region”) close to and the other (“far-region”) far away from the $P_x$ selection $\eta$ window. The away-side jet contributes to the close-region but not as much to the far-region due to the large $\eta$ gap, while the flow contributions are equal. Assuming the $\Delta\phi$ shape of jet-like correlations does not depend on $\Delta\eta$, the correlation difference measures the away-side jet shape where the anisotropic flow background is cleanly subtracted.

The away-side jet correlation width is studied in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}}=200$ GeV as a function of centrality and associated particle $p_T$. The width is found to increase with centrality at modest to high associated particle $p_T$. The increase can arise from jet-medium modifications, event averaging of away-side jets deflected by medium flow, and/or simply nuclear $k_T$ broadening. To further discriminate various physics mechanisms, a three-particle correlation analysis is conducted with robust flow background subtraction also using data. Based on this analysis we discuss possible physics mechanisms of away-side broadening of jet-like correlations.

Presentation type Oral

Primary author

Kun Jiang (University of Science and Technology of China)

Presentation Materials