Jet quenching is the process of color-charged partons losing energy via interactions with quark-gluon
plasma droplets created in heavy-ion collisions. The collective expansion of such droplets is well described
by viscous hydrodynamics. Similar evidence of collectivity is consistently observed in smaller collision
systems, including pp and p þ Pb collisions. In contrast, while jet quenching is observed in Pb þ Pb
collisions, no evidence has been found in these small systems to date, raising fundamental questions about
the nature of the system created in these collisions. The ATLAS experiment at the Large Hadron Collider
has measured the yield of charged hadrons correlated with reconstructed jets in 0.36 nb−1 of p þ Pb and
3.6 pb−1 of pp collisions at 5.02 TeV. The yields of charged hadrons with pch
T > 0.5 GeV near and
opposite in azimuth to jets with pjet
T > 30 or 60 GeV, and the ratios of these yields between p þ Pb and pp
collisions, IpPb, are reported. The collision centrality of p þ Pb events is categorized by the energy
deposited by forward neutrons from the struck nucleus. The IpPb values are consistent with unity within a
few percent for hadrons with pch
T > 4 GeV at all centralities. These data provide new, strong constraints
that preclude almost any parton energy loss in central p þ Pb collisions.BSF-NSFCEA-DRFCantons of Bern and GenevaDNSRC
IN2P3-CNRSEU-ESFGenT Programmes Generalitat Valenciana, SpainGridKAINFN-CNAFLa Caixa Banking FoundationMIZŠMNENDGFNDGFNorwegian Financial Mechanism
2014-2021PROMETEORGCUNCE
SCI/013UNCE
SCI/013Wallenberg FoundationU.S. Department of EnergyAlexander von Humboldt-StiftungAlabama Space Grant ConsortiumBrookhaven National LaboratoryCRC Health GroupCanarieKarlsruhe Institute of TechnologyH2020 Marie Skłodowska-Curie ActionsMultiple Sclerosis Scientific Research FoundationCERNCompute CanadaGöran Gustafssons StiftelserNatural Sciences and Engineering Research Council of CanadaNational Research Council CanadaCanada Foundation for InnovationScience and Technology Facilities CouncilLeverhulme TrustEuropean Research CouncilEuropean Cooperation in Science and TechnologyAustralian Research CouncilNational Stroke FoundationNeurosurgical Research FoundationHelmholtz-GemeinschaftHelmholtz-GemeinschaftMinerva FoundationDeutsche ForschungsgemeinschaftAgence Nationale de la RechercheJapan Society for the Promotion of ScienceMinistry of Education, Culture, Sports, Science and TechnologySchweizerischer Nationalfonds zur Förderung der Wissenschaftlichen ForschungDanmarks GrundforskningsfondFundação de Amparo à Pesquisa do Estado de São PauloNational Natural Science Foundation of ChinaFundação para a Ciência e a TecnologiaBundesministerium für Bildung und ForschungChinese Academy of SciencesAustrian Science FundGeneralitat de CatalunyaMinistry of Science and Technology of the People's Republic of ChinaAgencia Nacional de Promoción Científica y TecnológicaNederlandse Organisatie voor Wetenschappelijk OnderzoekBundesministerium für Wissenschaft, Forschung und WirtschaftConselho Nacional de Desenvolvimento Científico e TecnológicoNella and Leon Benoziyo Center for Neurological Diseases, Weizmann Institute of ScienceIsrael Science FoundationInstituto Nazionale di Fisica NucleareNarodowe Centrum NaukiJavna Agencija za Raziskovalno Dejavnost RSMinistarstvo Prosvete, Nauke i Tehnološkog RazvojaMinisterio de Ciencia e InnovaciónCentre National pour la Recherche Scientifique et TechniqueStaatssekretariat für Bildung, Forschung und InnovationHorizon 2020British Columbia Knowledge Development FundEuropean Regional Development FundDefence Science InstituteNarodowa Agencja Wymiany AkademickiejInstitutul de Fizică AtomicăAgencia Nacional de Investigación y DesarrollRoyal Society of South Australi
