Charged-particle production as a function of the relative transverse activity classifier in pp, p–Pb, and Pb–Pb collisions at the LHC

The ALICE collaboration [email protected]

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Abstract

Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum pTtrig in the range 8 <pTtrig< 15 GeV/c. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, RT=NchT/NchT, is used to group events according to their UE activity, where NchT is the charged-particle multiplicity per event in the transverse region and NchT is the mean value over the whole analysed sample. The energy dependence of the RT distributions in pp collisions at s = 2.76, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle pT spectra as a function of RT in the three azimuthal regions in pp, p–Pb, and Pb–Pb collisions at sNN = 5.02 TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p–Pb).

Original languageEnglish
Article number56
JournalJournal of High Energy Physics
Volume2024
Issue number1
DOIs
StatePublished - Jan 2024

Funding

The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration. The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (Finep), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Bulgarian Ministry of Education and Science, within the National Roadmap for Research Infrastructures 2020-2027 (object CERN), Bulgaria; Ministry of Education of China (MOEC) , Ministry of Science & Technology of China (MSTC) and National Natural Science Foundation of China (NSFC), China; Ministry of Science and Education and Croatian Science Foundation, Croatia; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research | Natural Sciences, the VILLUM FONDEN and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l’Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium für Bildung und Forschung (BMBF) and GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Commission, Government of India (UGC) and Council of Scientific and Industrial Research (CSIR), India; National Research and Innovation Agency - BRIN, Indonesia; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS) KAKENHI, Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección General de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Católica del Perú, Peru; Ministry of Education and Science, National Science Centre and WUT ID-UB, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics, Ministry of Research and Innovation and Institute of Atomic Physics and Universitatea Nationala de Stiinta si Tehnologie Politehnica Bucuresti, Romania; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; Suranaree University of Technology (SUT), National Science and Technology Development Agency (NSTDA) and National Science, Research and Innovation Fund (NSRF via PMU-B B05F650021), Thailand; Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America. In addition, individual groups or members have received support from: European Research Council, Strong 2020 - Horizon 2020 (grant nos. 950692, 824093), European Union; Academy of Finland (Center of Excellence in Quark Matter) (grant nos. 346327, 346328), Finland.

FundersFunder number
Council of Scientific and Industrial Research, India
State Committee of Science and World Federation
Ministry of Communications and High Technologies
Ministry of Education and Science
Department of Atomic Energy, Government of India
National Academy of Sciences of Ukraine
National Science and Technology Development Agency
National Research Foundation of Korea
Villum Fonden
National Science, Research and Innovation Fund
Ministry of Education of the People's Republic of China
Narodowe Centrum Nauki
University Grants Commission
Institut National de Physique Nucléaire et de Physique des Particules
Science and Technology Facilities Council
Institute of Atomic Physics and Universitatea Nationala de Stiinta si Tehnologie Politehnica Bucuresti
General Secretariat for Research and Technology, Ministry of Education, Research and Religions
Japan Society for the Promotion of Science
Ministry of Education and Science
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Korea Institute of Science and Technology Information
Knut och Alice Wallenbergs Stiftelse
Ministry of Science and Education and Croatian Science Foundation
Instituto Nazionale di Fisica Nucleare
Financiadora de Estudos e Projetos
Ontario Ministry of Research and Innovation
Department of Science and Technology, Ministry of Science and Technology, India
Consejo Nacional de Ciencia y Tecnología
Helsinki Institute of Physics
Norges Forskningsråd
Yerevan Physics Institute
Natur og Univers, Det Frie Forskningsråd
Centre National de la Recherche Scientifique
Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
Bundesministerium für Bildung und Forschung
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
Danmarks Grundforskningsfond
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Suranaree University of Technology
Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear
Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu
Nemzeti Kutatási Fejlesztési és Innovációs Hivatal
European Commission
GSI Helmholtzzentrum für Schwerionenforschung
U.S. Department of Energy
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Nuclear Research Center
WUT ID-UB
Institutul de Fizică Atomică
Ministry of Science and Technology of the People's Republic of China
Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic
Ministry of Education, Science, Research and Sport
Fondo de Cooperación Internacional en Ciencia y Tecnología
Universidade Federal do Rio Grande do Sul
Österreichischen Akademie der Wissenschaften
University Grants Commission, Government of India
European Research Council
National Research Foundation
Badan Riset dan Inovasi Nasional
Ministry of Higher Education and Scientific Research
CERN
Nuclear Physics
Vetenskapsrådet
Österreichische Nationalstiftung für Forschung, Technologie und Entwicklung
Ministry of Education, Culture, Sports, Science and Technology
National Natural Science Foundation of China
NSRFB05F650021
Horizon 2020824093, 950692
Horizon 2020
Research Council of Finland346328, 346327
Research Council of Finland
Austrian Science FundM 2467-N36
Austrian Science Fund

    Keywords

    • Hadron-Hadron Scattering
    • Hard Scattering
    • Multi-Parton Interactions

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