Measurement of jet fragmentation into charged particles in pp and PbPb collisions at root s(NN)=2.76 TeV
FMSR (Austria) ; Fonds de la Recherche Scientifique (FNRS) ; FWO (Belgium) ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; MES (Bulgaria) ; Organisation Européenne pour la Recherche Nucléaire (CERN) ; Chinese Academy of Sciences (CAS) ; MoST (China) ; National Natural Science Foundation of China (NSFC) ; COLCIENCIAS (Colombia) ; MSES (Croatia) ; Research Promotion Foundation (RPF) ; MoER ; European Regional Development Fund (ERDF) ; Academy of Finland ; MEC ; Helsinki Institute of Physics (HIP) ; CEA ; Institut national de physique nucléaire et de physique des particules (IN2P3/CNRS) ; Bundesministerium für Bildung und Forschung (BMBF) ; Deutsche Forschungsgemeinschaft (DFG) ; HGF (Germany) ; General Secretariat for Research and Technology (GSRT) ; Hungarian Scientific Research Fund (OTKA) ; NKTH (Hungary) ; Department of Atomic Energy (DAE) - India ; Department of Science and Technology (DST) - India ; Institute for Research in Fundamental Sciences (IPM) ; Science Foundation Ireland (SFI) ; Istituto Nazionale di Fisica Nucleare (INFN) ; NRF ; WCU (Korea) ; LAS (Lithuania) ; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV) ; Consejo Nacional de Ciencia y Tecnología (CONACYT) ; SEP (Mexico) ; SEP, and UASLP-FAI (Mexico) ; MSI (New Zealand) ; Pakistan Atomic Energy Commission (PAEC) ; MSHE (Poland) ; NSC (Poland) ; Fundação para a Ciência e a Tecnologia (FCT) ; Joint Institute for Nuclear Research (JINR) ; MON (Russia) ; Rosatom State Atomic Energy Corporation (ROSATOM) ; RAS (Russia) ; Russian Foundation for Basic Research (RFBR) ; Ministry of Science and Technological Development (MSTD) - Serbia ; MICINN (Spain) ; Centro Nacional de Física de Partículas, Astropartículas y Nuclear (CPAN) ; Swiss Funding Agencies (Switzerland) ; NSC (Taipei) ; Scientific and Technological Research Council of Turkey (TUBITAK) ; Türkiye Atom Enerjisi Kurumu (TAEK) ; Science and Technology Facilities Council (STFC) ; Department of Energy (DOE) and National Science Foundation (NSF) - USA ; Marie-Curie programme ; European Research Council (European Union) ; Leventis Foundation ; A. P. Sloan Foundation ; Alexander von Humboldt Foundation ; Belgian Federal Science Policy Office ; Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium) ; Agentschap voor Innovatie door Wetenschap en Technologie (IWT) ; Council of Scientific and Industrial Research (CSIR) - India ; HOMING PLUS programme of Foundation for Polish Science ; European Union, Regional Development Fund ; MoER: SF0690030s09 ; Jet fragmentation in pp and PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair was studied using data collected with the CMS detector at the LHC. Fragmentation functions are constructed using charged-particle tracks with transverse momenta p(T) > 4 GeV/c for dijet events with a leading jet of p(T) > 100 GeV/c. The fragmentation functions in PbPb events are compared to those in pp data as a function of collision centrality, as well as dijet-p(T) imbalance. Special emphasis is placed on the most central PbPb events including dijets with unbalanced momentum, indicative of energy loss of the hard scattered parent partons. The fragmentation patterns for both the leading and subleading jets in PbPb collisions agree with those seen in pp data at 2.76 TeV. The results provide evidence that, despite the large parton energy loss observed in PbPb collisions, the partition of the remaining momentum within the jet cone into high-p(T) particles is not strongly modified in comparison to that observed for jets in vacuum.