Girth and groomed radius of jets recoiling against isolated photons in lead-lead and proton-proton collisions at $$\sqrt{s_{NN}} = 5.02$$ TeV
This Letter presents the first measurements of the groomed jet radius Rg and the jet girth g in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables Rg and g provide a quantitative measure of how narrow or broad a jet is. The analysis uses PbPb and pp data samples with integrated luminosities of 1.7 nb-1 and 301 pb-1 , respectively, collected with the CMS experiment in 2018 and 2017. Events are required to have a photon with transverse momentum $$p^{γ}_{T} > 100$$ GeV and at least one jet back-to-back in azimuth with respect to the photon and with transverse momentum $$p^{jet}_{T}$$ such that $$p^{jet}_{T}/p^{γ}_{T} > 0.4$$ . The measured Rg and g distributions are unfolded to the particle level, which facilitates the comparison between the PbPb and pp results and with theoretical predictions. It is found that jets with $$p^{jet}_{T}/p^{γ}_{T} > 0.8$$ , i.e., those that closely balance the photon $$p^{γ}_{T}$$ , are narrower in PbPb than in pp collisions. Relaxing the selection to include jets with $$p^{jet}_{T}/p^{γ}_{T} > 0.4$$ reduces the narrowing of the angular structure of jets in PbPb relative to the pp reference. This shows that selection bias effects associated with jet energy loss play an important role in the interpretation of jet substructure measurements.
- Research Organization:
- AGH-UST, Cracow; AUM, Kuwait; Aachen, Tech. Hochsch.; Adiyaman U.; Ain Shams U., Cairo; Alabama U.; Andes U., Bogota; Annecy, LAPP; Antioquia U.; Antwerp U.; Athens U.; Bangalore, Indian Inst. Sci.; Bari U.; Baylor U.; Beihang U.; Beijing, Inst. High Energy Phys.; Belgrade U.; Bethel Coll.; Bhubaneswar, Inst. Phys.; Bhubaneswar, NISER; Bingöl U.; Bogazici U.; Boskovic Inst., Zagreb; Boston U.; Brandenburg Tech. U.; Bristol U.; British U. in Egypt; Brown U.; Brunel U.; Brussels U.; Bucharest, IFIN-HH; Budapest, RMKI; CERN; CHEP, Taegu; CINVESTAV, IPN; Cairo, Acad. Sci. Res. Tech.; Caltech; Cantabria Inst. of Phys.; Canterbury U.; Carnegie Mellon U.; Catholic U. America; Charles U.; Chonnam Natl. U.; Chulalongkorn U.; Colombo U.; Colorado U.; Conacyt, Mexico; Cornell U.; Cukurova U.; Cyprus U.; DESY; Debrecen, Inst. Nucl. Res.; Delhi U.; Democritos Nucl. Res. Ctr.; EKU KRC, Gyongyos; Ecole Polytechnique; Eotvos U.; Erzincan U.; Fayoum U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Florida Inst. Tech.; Florida State U.; Florida U.; Frascati; Fudan U.; GTU, Tbilisi; Gangneung-Wonju Natl. U.; Gent U.; Guglielmo Marconi U.; Hacettepe U.; Hamburg U.; Hanyang U.; Haute Alsace U.; Helsinki Inst. of Phys.; Helsinki U.; Helwan U.; IAS, Julich; IISER, Pune; INFN, Bari; INFN, Bologna; INFN, Catania; INFN, Florence; INFN, Genoa; INFN, Milan Bicocca; INFN, Naples; INFN, Padua; INFN, Pavia; INFN, Perugia; INFN, Pisa; INFN, Rome; INFN, Trieste; INFN, Turin; IP2I, Lyon; IPM, Tehran; IRFU, Saclay; Iberoamericana U.; Illinois U., Chicago; Imperial Coll., London; Indian Inst. Tech., Bhubaneswar; Indian Inst. Tech., Madras; Inst. Scintill. Mat., Kharkiv; Ioannina U.; Iowa U.; Isfahan Tech. U.; Istanbul Tech. U.; Istanbul U.; Istinye U., Istanbul; Johns Hopkins U.; KIT, Karlsruhe, EKP; Kafkas U.; Kansas State U.; Kansas U.; Karamanoglu Mehmetbey U., Karaman; Kharkov, KIPT; Korea U.; Kyung Hee U.; LIP, Lisbon; Lappeenranta U. Tech.; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Louvain U.; MIT; Madrid, Autonoma U.; Madrid, CIEMAT; Malaya U.; Marmara U.; Maryland U.; Middle East Tech. U., Ankara; Minnesota U.; Mississippi U.; Monash U.; Montenegro U.; NCBJ, Swierk; NICPB, Tallinn; Nanjing Normal U.; Naples U.; Natl. Tech. U., Athens; Naval Academy, Annapolis; Nebraska U.; Northeastern U.; Northwestern U.; Notre Dame U.; Ohio State U.; Oviedo U.; PSI, Villigen; Panjab U.; Peking U.; Pisa U.; Pisa, Scuola Normale Superiore; Princeton U.; Puebla U., Inst. Fis.; Puerto Rico U., Mayaguez; Purdue U.; Purdue U., Calumet; Quaid-i-Azam U.; Quito, Escuela Politecnica Natl.; Rice U.; Riga Tech. U.; Rio Grande do Sul U.; Rio de Janeiro State U.; Rio de Janeiro, CBPF; Rochester U.; Rockefeller U.; Ruhuna U.; Rutgers U., Piscataway; Rutherford; SUNY, Buffalo; SYSU, Guangzhou; Saha Inst.; San Francisco de Quito U.; Sejong U.; Seoul Natl. U.; Seoul U.; Sharif U. of Tech.; Sinop U.; Sofiya U.; Sofiya, Inst. Nucl. Res.; Sonora U.; Southampton U.; Split Tech. U.; Split U.; Stefan Meyer Inst. Subatomare Phys.; Strasbourg, IPHC; Sungkyunkwan U.; TIFR, Mumbai, DHEP; TU Vienna; Taiwan, Natl. Central U.; Taiwan, Natl. Taiwan U.; Tarapaca U.; Tashkent, IYF; Tennessee U.; Texas A&M U. Qatar, Doha; Texas A-M; Texas Tech.; Tsinghua U., Beijing; Turin U.; U. Campinas; U. Debrecen, Inst. Phys.; UC, Davis; UC, Riverside; UC, San Diego; UC, Santa Barbara; UCAS, Beijing; UCLA; USTM, Behshahr; Univ. of Colorado, Boulder, CO (United States); University Coll., Dublin; Unlisted; VINCA Inst. Nucl. Sci., Belgrade; Vanderbilt U.; Vienna, OAW; Vilnius U.; Virginia U.; Visva Bharati U.; Vrije U., Brussels; Warsaw U.; Warsaw U. of Tech.; Wayne State U.; Wisconsin U., Madison; Yerevan Phys. Inst.; Yildiz Tech. U.; Yonsei U.; Zewail City Sci. Technol., Giza; Zhejiang U.; Zurich U.; Zurich, ETH
- Sponsoring Organization:
- US Department of Energy; USDOE Office of Science (SC), High Energy Physics (HEP)
- Contributing Organization:
- The CMS Collaboration
- Grant/Contract Number:
- 89243024CSC000002; AC02-05CH11231; AC02-07CH11359; SC0010005
- OSTI ID:
- 3007018
- Report Number(s):
- CERN-EP-2024-073; CMS-HIN-23-001; FERMILAB-PUB-24-0338-CMS
- Journal Information:
- Physics Letters. B, Journal Name: Physics Letters. B Vol. 861; ISSN 0370-2693
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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