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

• Published in: arXiv.org
• Main Authors: Kauder, Kolja, the STAR Collaboration
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 13.04.2017
• Subjects: Collisions; Energy dissipation; Momentum; Recoil; Splitting
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1704.03046

One key difference in current energy loss models lies in the treatment of the Altarelli-Parisi, AP, splitting functions. It has been shown that the shared momentum fraction, henceforth called Jet Splitting Function \(z_g\) as determined by the SoftDrop grooming process can be made a Sudakov-safe measurement of the symmetrized AP functions in p+p collisions. The STAR collaboration presents the first z_g measurements at \(\sqrt{s_{NN}}=200\) GeV in p+p and Au+Au collisions, where in Au+Au we use the specific di-jet selection introduced in our previous momentum imbalance measurement. For a jet resolution parameter of \(R=0.4\), these di-jet pairs were found to be significantly imbalanced with respect to p+p, yet regained balance when all soft constituents were included. We find that within uncertainties there are no signs of a modified Jet Splitting Function on trigger or recoil sides of this di-jet selection.