Abstract
The global polarization of the Λ and Λ‾ hyperons is measured for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon's transverse momentum (pT) for the range of centrality 5-50%, 0.5<pT<5 GeV/c, and rapidity |y|<0.5. The hyperon global polarization averaged for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV is found to be consistent with zero, (PH)(%)≈0.01±0.06(stat.)±0.03(syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%.
| Original language | English |
|---|---|
| Article number | 044611 |
| Number of pages | 14 |
| Journal | Physical Review C |
| Volume | 101 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 20 Apr 2020 |
Funding
The global polarization of the Λ and Λ ¯ hyperons is measured for Pb-Pb collisions at s N N = 2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ( p T ) for the range of centrality 5–50%, 0.5 < p T < 5 GeV/ c , and rapidity | y | < 0.5 . The hyperon global polarization averaged for Pb-Pb collisions at s N N = 2.76 and 5.02 TeV is found to be consistent with zero, 〈 P H 〉 ( % ) ≈ 0.01 ± 0.06 (stat.) ± 0.03 (syst.) in the collision centrality range 15–50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01 % . Österreichischen Akademie der Wissenschaften 10.13039/501100001822 Austrian Science Fund 10.13039/501100002428 Österreichische Nationalstiftung für Forschung, Technologie und Entwicklung 10.13039/100010132 Conselho Nacional de Desenvolvimento Científico e Tecnológico 10.13039/501100003593 Financiadora de Estudos e Projetos 10.13039/501100004809 Fundação de Amparo à Pesquisa do Estado de São Paulo 10.13039/501100001807 Universidade Federal do Rio Grande do Sul 10.13039/501100004909 Ministry of Education of the People's Republic of China 10.13039/501100002338 National Natural Science Foundation of China 10.13039/501100001809 Hrvatska Zaklada za Znanost 10.13039/501100004488 Natur og Univers, Det Frie Forskningsråd 10.13039/100008394 Villum Fonden 10.13039/100008398 Danmarks Grundforskningsfond 10.13039/501100001732 Institut National de Physique Nucléaire et de Physique des Particules 10.13039/501100012441 Centre National de la Recherche Scientifique 10.13039/501100004794 Conseil Régional des Pays de la Loire 10.13039/501100013414 Bundesministerium für Bildung und Forschung 10.13039/501100002347 GSI Helmholtzzentrum für Schwerionenforschung GmbH 10.13039/501100010958 General Secretariat for Research and Technology 10.13039/501100003448 Nemzeti Kutatási Fejlesztési és Innovációs Hivatal 10.13039/501100011019 Department of Atomic Energy, Government of India 10.13039/501100001502 Department of Science and Technology, Ministry of Science and Technology 10.13039/501100001409 University Grants Commission 10.13039/501100001501 Central Mechanical Engineering Research Institute, Council of Scientific and Industrial Research 10.13039/501100012522 Lembaga Ilmu Pengetahuan Indonesia 10.13039/501100009728 Instituto Nazionale di Fisica Nucleare 10.13039/501100004007 Ministry of Education, Culture, Sports, Science and Technology 10.13039/501100001700 Japan Society for the Promotion of Science 10.13039/501100001691 Consejo Nacional de Ciencia y Tecnología 10.13039/501100003141 Fondo de Cooperación Internacional en Ciencia y Tecnología 10.13039/501100007709 Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México 10.13039/501100006087 Nederlandse Organisatie voor Wetenschappelijk Onderzoek 10.13039/501100003246 COMSATS Institute of Information Technology 10.13039/100009529 Norges Forskningsråd 10.13039/501100005416 Pontificia Universidad Católica del Perú 10.13039/501100011871 Ministerstwo Nauki i Szkolnictwa Wyższego 10.13039/501100004569 National Research Foundation of Korea 10.13039/501100003725 Joint Institute for Nuclear Research 10.13039/501100003822 Ministry of Education and Science of the Russian Federation 10.13039/501100003443 Russian Science Foundation 10.13039/501100006769 Russian Foundation for Basic Research 10.13039/501100002261 Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky 10.13039/501100003193 Vetenskapsrådet 10.13039/501100004359 CERN 10.13039/100012470 Suranaree University of Technology 10.13039/501100004352 National Science and Technology Development Agency 10.13039/501100004192 Office of the Higher Education Commission 10.13039/100012527 Türkiye Atom Enerjisi Kurumu 10.13039/100010440 National Academy of Sciences of Ukraine 10.13039/501100004742 Science and Technology Facilities Council 10.13039/501100000271 National Science Foundation 10.13039/100000001 The ALICE Collaboration thanks 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 centers 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; 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), Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS) and Région des Pays de la Loire, 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; Indonesian Institute of Science, Indonesia; Centro Fermi–Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science and Technology, Nagasaki Institute of Applied Science (IIST), 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 Science and Higher Education and National Science Centre, 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 and Ministry of Research and Innovation and Institute of Atomic Physics, Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federation, National Research Centre Kurchatov Institute, Russian Science Foundation and Russian Foundation for Basic Research, Russia; 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 (NSDTA) and Office of the Higher Education Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), 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), USA.