# 11th international workshop on High-pT Physics in the RHIC & LHC Era

12-15 April 2016
BNL Physics Building
US/Eastern timezone

## Di-Jet Imbalance Measurements in Central Au+Au Collisions at $\sqrt{s_{NN}}=$200~GeV from STAR

14 Apr 2016, 16:00
30m
Large Seminar Room (BNL Physics Building)

### Speaker

Mr Kolja Kauder (Wayne State University)

### Description

The transverse momentum di-jet imbalance $A_J$ presents a powerful and robust tool to explore the strong medium modification that has been found in central 200 GeV Au+Au collisions at RHIC in numerous statistical observables. In the presented study, we focus on a set of di-jets biased toward imbalance by requiring $p_T>20$~GeV/$c$ for the leading jet, $p_T>10$~GeV/$c$ for the sub-leading jet, and $p_T>2$~GeV/$c$ for the constituents of the jets as well as a 5 GeV particle in the calorimeter to trigger the event. This constituent cut drastically reduces the underlying heavy ion background and leads to di-jet event-by-event selection. We then examine the evolution of $A_J$ when reclustering these same di-jets with lower constituent cuts, until, at 200 MeV and for a resolution parameter of $R=0.4$, all lost energy is seemingly recovered and the balance is restored to the level of $pp$ collisions. In addition, a variation of $R$ gives access to the angular dependence of jet energy loss. Comparing these results to established LHC measurements enables new discussions and constraints of the underlying energy loss mechanisms that lead to the observed softening and broadening of jets in the strongly interacting medium created in heavy-ion collisions.

### Primary author

Mr Kolja Kauder (Wayne State University)

 Slides