Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina, YerPhI, Armenia, ARC, Australia, BMWFW and FWF, Austria, ANAS, Azerbaijan, SSTC, Belarus, CNPq and FAPESP, Brazil, NSERC, NRC, and CFI, Canada, CERN and ANID, Chile, CAS, MOST, and NSFC, China, COLCIENCIAS, Colombia, MSMT CR, MPO CR, and VSC CR, Czech Republic, DNRF and DNSRC, Denmark, IN2P3-CNRS and CEA-DRF/IRFU, France, SRNSFG, Georgia, BMBF, HGF, and MPG, Germany, GSRT, Greece, RGC and Hong Kong SAR, China, ISF and Benoziyo Center, Israel, INFN, Italy, MEXT and JSPS, Japan, CNRST, Morocco, NWO, Netherlands, RCN, Norway, MNiSW and NCN, Poland, FCT, Portugal, MNE/IFA, Romania, JINR, MES of Russia, and NRC KI, Russian Federation, MESTD, Serbia, MSSR, Slovakia, ARRS and MIZS, Slovenia, DST/NRF, South Africa, MICINN, Spain, SRC and Wallenberg Foundation, Sweden, SERI, SNSF, and Cantons of Bern and Geneva, Switzerland, MOST, Taiwan, TAEK, Turkey, STFC, United Kingdom, DOE and NSF, USA. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada, CRC and IVADO, Canada, Beijing Municipal Science & Technology Commission, China, COST, ERC, ERDF, Horizon 2020, and Marie Sklodowska-Curie Actions, European Union, Investissements d'Avenir Labex, Investissements d'Avenir Idex and ANR, France, DFG and AvH Foundation, Germany, Herakleitos, Thales, and Aristeia programs cofinanced by EU-ESF and the Greek NSRF, Greece, BSF-NSF and GIF, Israel, La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya, and PROMETEO and GenT Programmes Generalitat Valenciana, Spain, Goran Gustafssons Stiftelse, Sweden, The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK), and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [67].
Two-particle long-range azimuthal correlations are measured in photonuclear collisions using 1.7 nb−1 of 5.02 TeV Pb+Pb collision data collected by the ATLAS experiment at the CERN Large Hadron Collider. Candidate events are selected using a dedicated high-multiplicity photonuclear event trigger, a combination of information from the zero-degree calorimeters and forward calorimeters, and from pseudorapidity gaps constructed using calorimeter energy clusters and charged-particle tracks. Distributions of event properties are compared between data and Monte Carlo simulations of photonuclear processes. Two-particle correlation functions are formed using charged-particle tracks in the selected events, and a template-fitting method is employed to subtract the nonflow contribution to the correlation. Significant nonzero values of the secondand third-order flow coefficients are observed and presented as a function of charged-particle multiplicity and transverse momentum. The results are compared with flow coefficients obtained in proton-proton and proton-lead collisions in similar multiplicity ranges, and with theoretical expectations. The unique initial conditions present in this measurement provide a new way to probe the origin of the collective signatures previously observed only in hadronic collisions.
ANPCyT
Australian Research Council
Austrian Science Fund (FWF)
SSTC, Belarus
Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)
Natural Sciences and Engineering Research Council of Canada (NSERC) Canada Foundation for Innovation
National Natural Science Foundation of China (NSFC)
Departamento Administrativo de Ciencia, Tecnologia e Innovacion Colciencias
Ministry of Education, Youth & Sports - Czech Republic Czech Republic Government Czech Republic Government
Danish Natural Science Research Council
CEA-DRF/IRFU, France
Max Planck Society
RGC and Hong Kong SAR, China
Israel Science Foundation Benoziyo Center, Israel
Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science
CNRST, Morocco
Ministry of Science and Higher Education, Poland NCN, Poland
Portuguese Foundation for Science and Technology European Commission
Ministry of Education, Science & Technological Development, Serbia
Slovenian Research Agency - Slovenia MIZS, Slovenia
Spanish Government
Wallenberg Foundation, Sweden
SNSF Geneva, Switzerland
National Science Foundation (NSF)
BCKDF, Canada CANARIE, Canada
Beijing Municipal Science & Technology Commission
ERC, France ERDF, France Marie Sklodowska-Curie Actions, France French National Research Agency (ANR)
Alexander von Humboldt Foundation
EU-ESF, Greece Greek NSRF, Greece
BSF-NSF, Israel German-Israeli Foundation for Scientific Research and Development
CERCA Programme Generalitat de Catalunya, Spain PROMETEO, Spain GenT Programmes Generalitat Valenciana, Spain
Goran Gustafssons Stiftelse, Sweden
Royal Society of London Leverhulme Trust
YerPhI, Australia Armenia, Australia
BMWFW, Austria
ANAS, Belarus Azerbaijan, Belarus
Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ)
NRC, Canada
CERN, Chile ANID, Chile
Chinese Academy of Sciences Ministry of Science and Technology, China
DNRF, Denmark
Centre National de la Recherche Scientifique (CNRS)
SRNSFG, Germany Georgia, Germany
Federal Ministry of Education & Research (BMBF)
HGF, Germany
Greek Ministry of Development-GSRT
Istituto Nazionale di Fisica Nucleare (INFN)
Netherlands Organization for Scientific Research (NWO) Netherlands Government
RCN, Norway
MNE/IFA, Romania
JINR, Russia MES of Russia
NRC KI, Serbia Russian Federation, Serbia
MSSR, Slovakia
DST/NRF, South Africa
SRC, Sweden
SERI, Geneva, Switzerland Cantons of Bern Geneva, Switzerland
Ministry of Science and Technology, Taiwan
Ministry of Energy & Natural Resources - Turkey
UK Research & Innovation (UKRI)
Science & Technology Facilities Council (STFC)
United States Department of Energy (DOE)
Compute Canada, Canada CRC, Canada IVADO, Canada
COST, France Horizon 2020, France European Union, France
French National Research Agency (ANR)
German Research Foundation (DFG)
La Caixa Banking Foundation, Spain