Centrality dependence of particle production in p-Pb collisions at root s(NN)=5.02 TeV
ALICE Collaboration (ukupan broj autora: 976)
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We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at root s(NN) = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N-part) or the number of nucleon-nucleon binary collisions (N-coll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an... alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N-part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-pT the p-Pb spectra are found to be consistent with the pp spectra scaled by N-coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.
Source:Physical Review C, 2015, 91, 6
- Worldwide LHC Computing Grid (WLCG) collaboration, State Committee of Science, World Federation of Scientists (WFS), Swiss Fonds Kidagan, Armenia, 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), National Natural Science Foundation of China (NSFC), Chinese Ministry of Education (CMOE), Ministry of Science and Technology of China (MSTC), Ministry of Education and Youth of the Czech Republic, Danish Natural Science Research Council, Carlsberg Foundation, Danish National Research Foundation, European Research Council, Helsinki Institute of Physics, Academy of Finland, French CNRS-IN2P3, Region Pays de Loire, Region Alsace, Region Auvergne, CEA, France, German Bundesministerium fur Bildung, Wissenschaft, Helmholtz Association, General Secretariat for Research and Technology, Ministry of Development, Greece, Hungarian Orszagos Tudomanyos Kutatasi Alappgrammok (OTKA), National Office for Research and Technology (NKTH), Department of Atomic Energy and the Department of Science and Technology of the Government of India, Istituto Nazionale di Fisica Nucleare (INFN), Centro Fermi-Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Italy, Joint Institute for Nuclear Research, Dubna, National Research Foundation of Korea (NRF), Consejo Nacional de Cienca y Tecnologia (CONACYT), Direccion General de Asuntos del Personal Academico (DGAPA), Mexico, Amerique Latine Formation academique-European Commission (ALFA-EC), EPLANET Program (European Particle Physics Latin American Network) Stichting voor Fundamenteel Onderzoek der Materie (FOM), Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands, Research Council of Norway (NFR), Polish Ministry of Science and Higher Education, National Science Center, Poland, Ministry of National Education/Institute for Atomic Physics and Consiliul National al Cercetarii Stiintifice-Executive Agency for Higher Education Research Development and Innovation Funding (CNCS-UEFISCDI)-Romania, Ministry of Education and Science of the Russian Federation, Russian Academy of Sciences, Russian Federal Agency of Atomic Energy, Russian Federal Agency for Science and Innovations, Russian Foundation for Basic Research, Ministry of Education of Slovakia, Department of Science and Technology, South Africa, Centro de Investigaciones Energeticas, Medioam-bientales y Tecnologicas (CIEMAT), E-Infrastructure shared between Europe and Latin America (EELA), Ministerio de Economia y Competitividad (MINECO) of Spain, Xunta de Galicia (Conselleria de Educacion), Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Cubaenergia, Cuba, IAEA (International Atomic Energy Agency), Swedish Research Council (VR), Knut and Alice Wallenberg Foundation (KAW), Ukraine Ministry of Education and Science, United Kingdom Science and Technology Facilities Council (STFC), United States Department of Energy, United States National Science Foundation, State of Texas, State of Ohio, Ministry of Science, Education and Sports of Croatia, Unity through Knowledge Fund, Croatia, Council of Scientific and Industrial Research (CSIR), New Delhi, India, Forschung und Technologie (BMBF), MEXT Japan