Evidence for Top Quark Production in Nucleus-Nucleus Collisions

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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. © 2020 CERN.

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dc.contributor.authorSirunyan, A.M.
dc.contributor.authorTumasyan, A.
dc.contributor.authorAdam, W.
dc.contributor.authorAmbrogi, F.
dc.contributor.authorBergauer, T.
dc.contributor.authorDragicevic, M.
dc.contributor.authorErö, J.
dc.contributor.authorEscalante Del Valle, A.
dc.contributor.authorFrühwirth, R.
dc.contributor.authorJeitler, M.
dc.contributor.authorKrammer, N.
dc.contributor.authorLechner, L.
dc.contributor.authorLiko, D.
dc.contributor.authorMadlener, T.
dc.contributor.authorMikulec, I.
dc.contributor.authorRad, N.
dc.contributor.authorSchieck, J.
dc.contributor.authorSchöfbeck, R.
dc.contributor.authorSpanring, M.
dc.contributor.authorTempl, S.
dc.contributor.authorWaltenberger, W.
dc.contributor.authorWulz, C.-E.
dc.contributor.authorZarucki, M.
dc.contributor.authorChekhovsky, V.
dc.contributor.authorLitomin, A.
dc.contributor.authorMakarenko, V.
dc.contributor.authorSuarez Gonzalez, J.
dc.contributor.authorDarwish, M.R.
dc.contributor.authorDe Wolf, E.A.
dc.contributor.authorDi Croce, D.
dc.contributor.authorJanssen, X.
dc.contributor.authorKello, T.
dc.contributor.authorLelek, A.
dc.contributor.authorPieters, M.
dc.contributor.authorRejeb Sfar, H.
dc.contributor.authorVan Haevermaet, H.
dc.contributor.authorVan Mechelen, P.
dc.contributor.authorVan Putte, S.
dc.contributor.authorVan Remortel, N.
dc.contributor.authorBlekman, F.
dc.contributor.authorBols, E.S.
dc.contributor.authorChhibra, S.S.
dc.contributor.authorD’Hondt, J.
dc.contributor.authorDe Clercq, J.
dc.contributor.authorLontkovskyi, D.
dc.contributor.authorLowette, S.
dc.contributor.authorMarchesini, I.
dc.contributor.authorMoortgat, S.
dc.contributor.authorPython, Q.
dc.contributor.authorTavernier, S.
dc.date.accessioned2026-10-18T20:28:10.783201039Z
dc.date.available2026-10-18T20:28:10.783201039Z
dc.date.issued2020
dc.description.abstractUltrarelativistic 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. © 2020 CERN.
dc.description.sponsorshipWe 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).
dc.identifier.doi10.1103/physrevlett.125.222001
dc.identifier.issn0031-9007
dc.identifier.issue22
dc.identifier.pmid33315428
dc.identifier.scopus2-s2.0-85097318502
dc.identifier.startpage222001
dc.identifier.urihttps://rdlopen.rawdatalibrary.net/r/ebyu/13338
dc.identifier.volume125
dc.language.isoen
dc.publisherAmerican Physical Society
dc.relation.ispartofPhysical Review Letters
dc.rightsinfo:eu-repo/semantics/openAccess
dc.subjectColliding beam accelerators
dc.subjectNuclear reactions
dc.subjectQuantum theory
dc.subjectTellurium compounds
dc.subjectBottom quarks
dc.subjectCondition
dc.subjectEarly universe
dc.subjectNucleus-nucleus collision
dc.subjectQuantum chromodynamics
dc.subjectQuark production
dc.subjectQuark-gluon plasma
dc.subjectThermodynamical
dc.subjectTop quarks
dc.subjectUltrarelativistic heavy ion collision
dc.subjectarticle
dc.subjectelectron
dc.subjectexpectation
dc.subjecthuman tissue
dc.subjectlepton
dc.subjectnucleon
dc.subjectprediction
dc.subjectquark
dc.subjectHeavy ions
dc.titleEvidence for Top Quark Production in Nucleus-Nucleus Collisions
dc.typeArticle
dspace.entity.typePublication
rdl.citation.scopus24
rdl.oa.statusgold
rdl.source.indexSCOPUS