Journal
PHYSICAL REVIEW LETTERS
Volume 128, Issue 17, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.128.172005
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Funding
- 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]
- Nationalstiftung fur Forschung, Technologie und Entwicklung, Austria
- Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)
- Financiadora de Estudos e Projetos (Finep)
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)
- Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
- Ministry of Education of China (MOEC), China
- Ministry of Science and Technology of China (MSTC), China
- National Natural Science Foundation of China (NSFC), China
- Ministry of Science and Education and Croatian Science Foundation, Croatia
- Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Cubaenergia, Cuba
- Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic
- Danish Council for Independent Research | Natural Sciences, Denmark
- VILLUM FONDEN, Denmark
- Danish National Research Foundation DNRF, Denmark
- Helsinki Institute of Physics (HIP), Finland
- Commissariat `a l'Energie Atomique (CEA), France
- Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), France
- Centre National de la Recherche Scientifique (CNRS), France
- Bundesministerium fur Bildung und Forschung (BMBF), Germany
- GSI Helmholtzzentrum fur 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)
- Council of Scientific and Industrial Research (CSIR), India
- Indonesian Institute of Science, Indonesia
- Istituto Nazionale di Fisica Nucleare (INFN), Italy
- Institute for Innovative Science and Technology, Japan
- Nagasaki Institute of Applied Science (IIST), Japan
- Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
- Japan Society for the Promotion of Science (JSPS) KAKENHI, Japan
- Consejo Nacional de Ciencia (CONACYT) y Tecnologia, through Fondo de Cooperacion Internacional en Ciencia y Tecnologia (FONCICYT), Mexico
- Direccion General de Asuntos del Personal Academico (DGAPA), Mexico
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands
- Research Council of Norway, Norway
- Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan
- Pontificia Universidad Catolica del Peru, Peru
- Ministry of Education and Science, Poland
- National Science Centre, Poland
- WUT ID-UB, Poland
- Korea Institute of Science and Technology Information, Republic of Korea
- National Research Foundation of Korea (NRF), Republic of Korea
- Ministry of Education and Scientific Research, Romania
- Institute of Atomic Physics, Romania
- Joint Institute for Nuclear Research (JINR), Russia
- Ministry of Education and Science of the Russian Federation, Russia
- National Research Centre Kurchatov Institute, Russia
- Russian Science Foundation, Russia
- 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), Sweden
- Knut and Alice Wallenberg Foundation (KAW), Sweden
- European Organization for Nuclear Research, Switzerland
- Suranaree University of Technology (SUT), Thailand
- National Science and Technology Development Agency (NSDTA), Thailand
- Office of the Higher Education Commission under NRU project of Thailand, 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), United States of America
- United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America
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The study measured the polarization of Lambda and (Lambda) over bar hyperons along the beam direction in Pb-Pb collisions, showing a non-zero P-z for hyperons in these collisions. This provides sensitivity to competing contributions from thermal and shear-induced vorticity, as well as the phase where polarization is acquired.
The polarization of the Lambda and (Lambda) over bar hyperons along the beam (z) direction, P-z, has been measured in Pb-Pb collisions at root s(NN) = 5.02 TeV recorded with ALICE at the Large Hadron Collider (LHC). The main contribution to P-z comes from elliptic flow-induced vorticity and can be characterized by the second Fourier sine coefficient P-z,P-s2 = < P-z sin(2 phi - 2 Psi(2))>, where phi is the hyperon azimuthal emission angle and Psi(2) is the elliptic flow plane angle. We report the measurement of P-z,P-s2 for different collision centralities and in the 30%-50% centrality interval as a function of the hyperon transverse momentum and rapidity. The P-z,P-s2 is positive similarly as measured by the STAR Collaboration in Au-Au collisions at root s(NN) = 200 GeV, with somewhat smaller amplitude in the semicentral collisions. This is the first experimental evidence of a nonzero hyperon P-z in Pb-Pb collisions at the LHC. The comparison of the measured P-z,P-s2 with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear-induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase.
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