Abstract
Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10-6 sec, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon center-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production (σtt) via the selection of charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, σtt=2.54-0.74+0.84 and 2.03-0.64+0.71 μb, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions.
| Original language | English |
|---|---|
| Article number | 222001 |
| Journal | Physical Review Letters |
| Volume | 125 |
| Issue number | 22 |
| DOIs | |
| Publication status | Published - 24 Nov 2020 |
Bibliographical note
Publisher Copyright:© 2020 CERN.
Funding
We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Montenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); SEIDI, CPAN, PCTI, and FEDER (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).
| Funders | Funder number |
|---|---|
| CNRS/IN2P3 | |
| CPAN | |
| ERC IUT | |
| LNS | |
| MESTD | |
| MON | |
| MSES | |
| MSHE | |
| MoER | |
| PCTI | |
| STAR | |
| Swiss Funding Agencies | |
| TUBITAK | |
| ThEPCenter | |
| UASLP-FAI | |
| National Science Foundation | |
| U.S. Department of Energy | |
| Hispanics in Philanthropy | |
| CS Fund | |
| Maryland Ornithological Society | |
| Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) | |
| California Earthquake Authority | |
| Secretaría de Educación Pública | |
| Türkiye Atom Enerjisi Kurumu | |
| Louisiana Academy of Sciences | |
| Missouri University of Science and Technology | |
| CERN | |
| College of Arts and Sciences, University of Nebraska-Lincoln | |
| Norwegian Sequencing Centre | |
| Institute for the Promotion of Teaching Science and Technology | |
| Mountain Equipment Co-operative | |
| Science and Technology Facilities Council | GRIDPP |
| Royal Astronomical Society | |
| Ministry of Education - Singapore | |
| Department of Atomic Energy, Government of India | |
| Science Foundation Ireland | |
| Helmholtz-Gemeinschaft | |
| Deutsche Forschungsgemeinschaft | |
| Fundação de Amparo à Pesquisa do Estado de São Paulo | |
| National Natural Science Foundation of China | |
| Fundação para a Ciência e a Tecnologia | |
| Russian Foundation for Basic Research | |
| Coordenação de Aperfeiçoamento de Pessoal de Nível Superior | |
| Academy of Finland | |
| Bundesministerium für Bildung und Forschung | |
| Austrian Science Fund | |
| Fonds De La Recherche Scientifique - FNRS | |
| Fonds Wetenschappelijk Onderzoek | |
| Consejo Nacional de Ciencia y Tecnología | |
| General Secretariat for Research and Technology | |
| Conselho Nacional de Desenvolvimento Científico e Tecnológico | |
| Ministry of Science, ICT and Future Planning | |
| Ministry of Science and Technology | |
| National Research Foundation of Korea | |
| Joint Institute for Nuclear Research | |
| Instituto Nazionale di Fisica Nucleare | |
| National Science and Technology Development Agency | Thailand |
| Politechnika Poznańska | |
| Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul | |
| Secretaría de Educación Superior, Ciencia, Tecnología e Innovación | |
| Universiti Malaya | |
| Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro | |
| Ministry for Business Innovation and Employment | |
| National Academy of Sciences of Ukraine | |
| Ministry of Education and Science | |
| Institute for Research in Fundamental Sciences | |
| Benemérita Universidad Autónoma de Puebla | |
| Secretaría de Estado de Investigación, Desarrollo e Innovación | |
| European Regional Development Fund | |
| State Atomic Energy Corporation ROSATOM | |
| Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional | |
| Pakistan Atomic Energy Commission | |
| Department of Science and Technology, Government of West Bengal | |
| Ministry of Science,Technology and Research | |
| Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie | |
| Nemzeti Kutatási, Fejlesztési és Innovaciós Alap | |
| National Research Center "Kurchatov Institute" |