Title: 
Differential di-jet imbalance measurements in heavy-ion collisions at STAR

PAs:
Nicholas Elsey
Joern Putschke

Analysis note:
v1
v2
v3

Submitted analysis note:
https://drupal.star.bnl.gov/STAR/starnotes/private/psn0729

Target journal:
PRC

Abstract:
Previous results from STAR have shown via the di-jet imbalance ($A_J$) that “hard-core” jets, clustered with constituents with transverse momentum above 2 GeV/$c$ are significantly imbalanced compared to a p+p reference, while matched jets with the soft constituents included are balanced. We expand on this measurement by differentially varying the jetfinding parameters, including the hard-core cut and jet radius, and quantify the amount of modification for each variation with respect to a p+p reference using the $|A_J|$ observable. All di-jet definitions show significant imbalance in the hard-core jets. However, we observe a smooth transition from balanced matched di-jets at larger radii and higher hard-core constituent $p_T$ cut, to unbalanced matched di-jets at smaller radii and lower hard-core constituent $p_T$ cut. These results show that the systematic variation of the jet definition can be used to vary the amount of modification in the measured hard-core selected di-jets, and will help to constrain models of partonic energy loss in the medium. Assuming the observed modifications  by varying the di-jet definition can be explained in the context of a path-length dependent energy loss mechanism, these observations open up the opportunity for Jet Geometry Engineering at RHIC via control of the jet production vertices and orientation.

Paper proposal talk:
v1
v2

GPC:
Jana Bielcikova (chair)
Rosi Reed (english/grammar)
Nihar Sahoo (member at large)
Alex Jentsch (code QA)
Hanseul Oh (PWG rep)

GPC meetings:
10/3/2019
slides
minutes
11/21/2019
minutes

GPC comments:
Reed (9/24/19)
Sahoo (10/1/19)
Bielcikova (10/3/19)
Jentsch (10/3/19)
replies (11/19/19)
Oh (11/20/19)
replies (11/20/19)
Bielcikova (12/5/19)
Oh (12/5/19)
Jentsch (12/12/19)
replies (12/14/19)
Reed (01/14/20)
Oh (01/25/20)
Bielcikova (01/26/20)
Bielcikova (01/30/20)

Institutional review comments:
Lanzhou University
Panjab University
Purdue University
TAMU
UIC

Paper draft:
v0
v3
v4
v5
v6
v5-v6 diff
v7
v6-v7 diff
v8
v7-v8 diff
v9
v8-v9 diff
v10
v9-v10 diff

Paper code directory:
psn0729

Figures:

Tables:

Conclusions:
We have demonstrated that, by modifying the di-jet definition used during jet-finding, we can select jets that are relatively more or less modified compared to a p+p reference. This opens up the possibility of jet geometry engineering, and may help constrain the path length dependence of partonic energy loss in the QGP at RHIC. Further analysis with increased statistics to expand kinematic reach and reduced statistical errors, and comparison to jet quenching models are still needed.

Presented at:
Hard Probes 2018
International Workshop on high-p_T physics in the RHIC/LHC Era 2019