Measurement of isolated photon production in pp and PbPb collisions at sNN=2.76 TeV

This article is published Open Access at sciencedirect.com. It is distributed under the terms of the Creative Commons Attribution\ud
License 3.0.-- Chatrchyan, S. et al.Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |η|<1.44 and transverse energies E T between 20 and 80 GeV with the CMS detector at the LHC. The measured E T spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon E T-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities. © 2012 CERN.European Commission; Federal Ministry of Science, Research and Economy (Austria); National Fund for Scientific Research (Belgium); Research Foundation – Flanders; Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro; Fundação de Amparo à Pesquisa do Estado de São Paulo; Bulgarian Ministry of Education and Science; Centre National de la Recherche Scientifique (France); Commissariat à l'énergie atomique et aux énergies alternatives (France); Ministry of Science and Technology of the People's Republic of China; Chinese Academy of Sciences; National Natural Science Foundation of China; Colciencias (Colombia); Croatian Ministry of Science, Education and Sport; Academy of Finland; Helsinki Institute of Physics; Bundesministerium für Bildung und Forschung (Deutschland); Deutsche Forschungsgemeinschaft; Helmholtz Association; General Secretariat of Research and Technology (Greece); Hungarian Scientific Research Fund; National Office for Research and Technology (Hungary); Department of Atomic Energy (India); Department of Science and Technology (India); Council of Science and Industrial Research (India); Institute for Research in Fundamental Sciences (Iran); Science Foundation Ireland; Istituto Nazionale di Fisica Nucleare (Italia); Korean Ministry of Education, Science and Technology; Lithuanian Academy of Sciences; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (México); Consejo Nacional de Ciencia y Tecnología (México); Secretaría de Educación Pública (México); Universidad Autónoma de San Luis Potosí; Ministry of Science and Innovation (New Zealand); Ministry of Science and Higher Education and the National Science Centre (Poland); Fundação para a Ciência e a Tecnologia (Portugal); Joint Institute for Nuclear Research (Russia); Russian Academy of Sciences; Russian Foundation for Basic Research; Ministry of Education, Science and Technological Development (Serbia); Ministerio de Ciencia e Innovación (España); Swiss Funding Agencies; Swiss National Science Foundation; National Science Council (Taiwan); The Scientific and Technological Research Council of Turkey; Turkish Atomic Energy Authority; Science and Technology Facilities Council (UK); Department of Energy (US); National Science Foundation (US); A. G. Leventis Foundation; Alfred P. Sloan Foundation; Alexander von Humboldt Foundation; Foundation for Polish SciencePeer Reviewe