Differential measurements of jet substructure and partonic energy loss in Au + Au collisions at sNN =200 GeV

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The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in p+p and Au+Au collisions at sNN =200GeV. The substructure observables include SoftDrop groomed momentum fraction (zg), groomed jet radius (Rg), and subjet momentum fraction (zSJ) and opening angle (θSJ). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for p+p collisions and are compared to leading-order Monte Carlo models. The subjet θSJ distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in Au+Au collisions. We compare data from Au+Au collisions to those from p+p which are embedded in minimum-bias Au+Au events in order to include the effects of detector smearing and the heavy-ion collision underlying event. The subjet observables are shown to be more robust to the background than zg and Rg. We observe no significant modifications of the subjet observables within the two highest-energy, back-to-back jets, resulting in a distribution of opening angles and the splittings that are vacuumlike. We also report measurements of the differential dijet momentum imbalance (AJ) for jets of varying θSJ. We find no qualitative differences in energy loss signatures for varying angular scales in the range 0.1< θSJ<0.3, leading to the possible interpretation that energy loss in this population of high-momentum dijet pairs, is due to soft medium-induced gluon radiation from a single color charge as it traverses the medium.

Original languageEnglish
Article number044906
JournalPhysical Review C
Issue number4
StatePublished - Apr 2022

Bibliographical note

Funding Information:
We thank the RHIC Operations Group and RCF at BNL, the NERSC Center at LBNL, and the Open Science Grid consortium for providing resources and support. This work was supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science; the U.S. National Science Foundation; the Ministry of Education and Science of the Russian Federation; National Natural Science Foundation of China; Chinese Academy of Science; the Ministry of Science and Technology of China and the Chinese Ministry of Education; the Higher Education Sprout Project by Ministry of Education at NCKU; the National Research Foundation of Korea; Czech Science Foundation and Ministry of Education, Youth and Sports of the Czech Republic; Hungarian National Research, Development and Innovation Office; New National Excellency Programme of the Hungarian Ministry of Human Capacities; Department of Atomic Energy and Department of Science and Technology of the Government of India; the National Science Centre of Poland; the Ministry of Science, Education and Sports of the Republic of Croatia; RosAtom of Russia and German Bundesministerium für Bildung, Wissenschaft, Forschung and Technologie (BMBF) Helmholtz Association; Ministry of Education, Culture, Sports, Science, and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS).

Publisher Copyright:
© 2022 American Physical Society.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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