Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at root s(NN)=2.76 TeV
ALICE Collaboration (ukupan broj autora: 973)
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The effect of event background fluctuations on charged particle jet reconstruction in Pb-Pb collisions at root s(NN) = 2.76 TeV has been measured with the ALICE experiment. The main sources of non-statistical fluctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high p(t) particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti-k(t) jet finder. The influence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track p(t) between 0.15 GeV/c and 2 GeV/c. For embedded jets reconstructed from charged particles with p(t) GT 0.15 GeV/c, the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/c measured using the unbiased method. For a higher particle transverse... momentum threshold of 2 GeV/c, which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured fluctuations with steeply falling spectra.
Source:Journal of High Energy Physics, 2012, 3
- Calouste Gulbenkian Foundation from Lisbon and 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 under the European Community, Helsinki Institute of Physics, Academy of Finland, French CNRS-IN2P3, Region Pays de Loire, Region Alsace, Region Auvergne, CEA, France, German BMBF, Helmholtz Association, General Secretariat for Research and Technology, Ministry of Development, Greece, Hungarian OTKA, National Office for Research and Technology (NKTH), Department of Atomic Energy and Department of Science and Technology of the Government of India, Istituto Nazionale di Fisica Nucleare (INFN) of Italy, MEXT, Japan, Joint Institute for Nuclear Research, Dubna, National Research Foundation of Korea (NRF), CONACYT, DGAPA, Mexico, ALFA-EC, HELEN (High-Energy physics Latin-American-European 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 Authority for Scientific Research - NASR (Autoritatea Nationala pentru Cercetare Stiintifica - ANCS), Federal Agency of Science of the Ministry of Education and Science of Russian Federation, International Science and Technology Center, Russian Academy of Sciences, Russian Federal Agency of Atomic Energy, Russian Federal Agency for Science and Innovations, CERN-INTAS, Ministry of Education of Slovakia, Department of Science and Technology, South Africa, CIEMAT, EELA, Ministerio de Educacion y Ciencia of Spain, Xunta de Galicia (Conselleria de Educacion), CEADEN, Cubaenergia, Cuba, IAEA (International Atomic Energy Agency), Swedish Reseach 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