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>

Measurement of the Shared Momentum Fraction $z_g$ using Jet Reconstruction in p+p and Au+Au Collisions with STAR

25 Sep 2016, 11:00
Xiang-Yang Hall (East Lake International Conference Center)

Xiang-Yang Hall

East Lake International Conference Center

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


Kolja Kauder (Wayne State University)


Light quark and gluon jet quenching in heavy ion collisions is described within the overwhelming majority of models as resulting predominantly from pQCD-type gluon radiation,
but details of the underlying mechanisms differ greatly.
One key difference lies in the treatment of the Altarelli-Parisi, AP, splitting functions.
While in some models, such as Q-PYTHIA, the splitting functions are directly modified in the medium, this core component remains unchanged in others (e.g. YaJEM).
It has been shown that the shared momentum fraction $z_g$ can be made a Sudakov-safe measurement [1].
This quantity measures the $p_T$ ratio between the two dominant branches
as determined by the SoftDrop grooming process.

We will present the first study of $z_g$ measurements at top RHIC energy in p+p and Au+Au.
The focus will be on the specific di-jet selection introduced in our previous momentum imbalance measurement,
i.e. jets geometrically matched to ``hard core'' jets found using
only constituents above 2 GeV/$c$ and with a high tower above 5.5 GeV [2].
Such di-jet pairs were found to be significantly imbalanced with respect to p+p, yet regained balance when all soft constituents were included.
Individual examination of the splitting behavior of leading and recoil jet adds a new
dimension to this observation, and new input to energy loss models.

[1] A. J. Larkoski, S. Marzani and J. Thaler, Phys. Rev. D 91, no. 11, 111501 (2015) [arXiv:1502.01719 [hep-ph]].

[2] K. Kauder (STAR Collaboration), Nuclear and Particle Physics Proceedings, Hard Probes 2015

Presentation type Oral

Primary author

Kolja Kauder (Wayne State University)

Presentation Materials