Direct photon production at low transverse momentum in proton-proton collisions at s =2.76 and 8 TeV

ALICE Collaboration

doi:10.1103/PhysRevC.99.024912

Direct photon production at low transverse momentum in proton-proton collisions at s =2.76 and 8 TeV

ALICE Collaboration

Relativistic Nuclear Physics

Research output: Contribution to journal › Article › peer-review

25 Scopus citations

Abstract

Measurements of inclusive and direct photon production at midrapidity in pp collisions at s=2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.4<pT<10 GeV/c and 0.3<pT<16 GeV/c, respectively. Photons are detected with the electromagnetic calorimeter (EMCal) and via reconstruction of e+e- pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping pT interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio Rγ, which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio Rγ, as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full pT range, Rγ for pT>7 GeV/c is at least one σ above unity and consistent with expectations from next-to-leading order pQCD calculations.

Original language	English
Article number	024912
Journal	Physical Review C
Volume	99
Issue number	2
DOIs	https://doi.org/10.1103/PhysRevC.99.024912
State	Published - Feb 21 2019

Funding

We thank Werner Vogelsang and Jean-Francois Paquet for providing the NLO pQCD calculations. The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration. The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC), China; Ministry of Science, Education and Sport and Croatian Science Foundation, Croatia; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research Natural Sciences, the Carlsberg Foundation and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l'Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) and GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Commission, Government of India (UGC) and Council of Scientific and Industrial Research (CSIR), India; Indonesian Institute of Science, Indonesia; Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science and Technology, Nagasaki Institute of Applied Science (IIST), Japan Society for the Promotion of Science (JSPS) KAKENHI and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through Fondo de Cooperación Internacional en Ciencia y Tecnología (FONCICYT) and Dirección General de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Católica del Perú, Peru; Ministry of Science and Higher Education and National Science Centre, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics and Romanian National Agency for Science, Technology and Innovation, Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federation and National Research Centre Kurchatov Institute, Russia; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba and Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Spain; Swedish Research Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; National Science and Technology Development Agency (NSDTA), Suranaree University of Technology (SUT) and Office of the Higher Education Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America.

Funders	Funder number
Not added	ST/P004598/1, ST/P005438/1, 1796881, ST/L005670/1, ST/P004199/1, ST/P005047/1, 1657698, ALICE, ST/M00340X/1, ST/L005751/1, ST/M00158X/1, 1843572, ST/M001598/1
Austrian Academy of Sciences and Nationalstiftung für Forschung, Technologie und Entwicklung
Centre National de la Recherche Scientifique
Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fondo de Cooperación Internacional en Ciencia y Tecnología
Fundação de Amparo à Pesquisa do Estado de São Paulo
General Secretariat for Research and Technology, Ministry of Education, Research and Religions
Helsinki Institute of Physics
Indonesian Institute of Science, Indonesia
Institute of Atomic Physics and Romanian National Agency for Science, Technology and Innovation, Romania
Joint Institute for Nuclear Research
Ministry of Communications and High Technologies
Ministry of Education, Science, Research and Sport
Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic
Ministry of Science, Education and Sport and Croatian Science Foundation
NRU
National Natural Science Foundation of China
National Nuclear Research Center
National Research Foundation of Korea
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Science and Technology Facilities Council
State Committee of Science and World Federation
Suranaree University of Technology
Turkish Atomic Energy Agency
Universidade Federal do Rio Grande do Sul
University Grants Commission, Government of India
Yerevan Physics Institute
U.S. Department of Energy
Nuclear Physics
Natur og Univers, Det Frie Forskningsråd
Türkiye Atom Enerjisi Kurumu
Ministry of Higher Education and Scientific Research
CERN
Office of the Higher Education Commission
Institute for Innovative Science and Technology, Nagasaki Institute of Applied Science
Science and Technology Facilities Council	ST/N00261X/1, GRIDPP
National Research Foundation
Department of Science and Technology, Ministry of Science and Technology, India
Council of Scientific and Industrial Research, India
University Grants Commission
Department of Atomic Energy, Government of India
Japan Society for the Promotion of Science	15H03664, 17H01122, 16K17701
Ministry of Education, Culture, Sports, Science and Technology
Danmarks Grundforskningsfond
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Natural Science Foundation of China
Ministry of Education of the People's Republic of China
Bundesministerium für Bildung und Forschung
Carlsbergfondet
Ministry of Science and Technology of the People's Republic of China
Consejo Nacional de Ciencia y Tecnología
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Ministry of Education and Science of the Russian Federation
General Secretariat for Research and Technology
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Korea Institute of Science and Technology Information
National Research Foundation of Korea
Joint Institute for Nuclear Research
Instituto Nazionale di Fisica Nucleare
Knut och Alice Wallenbergs Stiftelse
National Science and Technology Development Agency
Narodowe Centrum Nauki
Suranaree University of Technology
Vetenskapsrådet
Ministerstwo Edukacji i Nauki
National Academy of Sciences of Ukraine
Centre National de la Recherche Scientifique
Financiadora de Estudos e Projetos
Universidade Federal do Rio Grande do Sul
Norges Forskningsråd
Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
Fondo de Cooperación Internacional en Ciencia y Tecnología
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
GSI Helmholtzzentrum für Schwerionenforschung
Nemzeti Kutatási Fejlesztési és Innovációs Hivatal
Institut National de Physique Nucléaire et de Physique des Particules
National Research Center "Kurchatov Institute"
Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear
Indian Institute of Space Science and Technology

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10.1103/PhysRevC.99.024912

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title = "Direct photon production at low transverse momentum in proton-proton collisions at s =2.76 and 8 TeV",

abstract = "Measurements of inclusive and direct photon production at midrapidity in pp collisions at s=2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.47 GeV/c is at least one σ above unity and consistent with expectations from next-to-leading order pQCD calculations.",

author = "{ALICE Collaboration} and S. Acharya and Acosta, {F. T.} and D. Adamov{\'a} and J. Adolfsson and Aggarwal, {M. M.} and {Aglieri Rinella}, G. and M. Agnello and N. Agrawal and Z. Ahammed and Ahn, {S. U.} and S. Aiola and A. Akindinov and M. Al-Turany and Alam, {S. N.} and Albuquerque, {D. S.D.} and D. Aleksandrov and B. Alessandro and {Alfaro Molina}, R. and Y. Ali and A. Alici and A. Alkin and J. Alme and T. Alt and L. Altenkamper and I. Altsybeev and C. Andrei and D. Andreou and Andrews, {H. A.} and A. Andronic and M. Angeletti and V. Anguelov and C. Anson and T. Anti{\v c}i{\'c} and F. Antinori and P. Antonioli and R. Anwar and N. Apadula and L. Aphecetche and H. Appelsh{\"a}user and S. Arcelli and R. Arnaldi and Arnold, {O. W.} and Arsene, {I. C.} and M. Arslandok and B. Audurier and A. Augustinus and R. Averbeck and F. Bock and Read, {K. F.} and Schmidt, {N. V.}",

note = "Publisher Copyright: {\textcopyright} 2019 CERN.",

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day = "21",

doi = "10.1103/PhysRevC.99.024912",

language = "English",

volume = "99",

journal = "Physical Review C",

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T1 - Direct photon production at low transverse momentum in proton-proton collisions at s =2.76 and 8 TeV

AU - ALICE Collaboration

AU - Acharya, S.

AU - Acosta, F. T.

AU - Adamová, D.

AU - Adolfsson, J.

AU - Aggarwal, M. M.

AU - Aglieri Rinella, G.

AU - Agnello, M.

AU - Agrawal, N.

AU - Ahammed, Z.

AU - Ahn, S. U.

AU - Aiola, S.

AU - Akindinov, A.

AU - Al-Turany, M.

AU - Alam, S. N.

AU - Albuquerque, D. S.D.

AU - Aleksandrov, D.

AU - Alessandro, B.

AU - Alfaro Molina, R.

AU - Ali, Y.

AU - Alici, A.

AU - Alkin, A.

AU - Alme, J.

AU - Alt, T.

AU - Altenkamper, L.

AU - Altsybeev, I.

AU - Andrei, C.

AU - Andreou, D.

AU - Andrews, H. A.

AU - Andronic, A.

AU - Angeletti, M.

AU - Anguelov, V.

AU - Anson, C.

AU - Antičić, T.

AU - Antinori, F.

AU - Antonioli, P.

AU - Anwar, R.

AU - Apadula, N.

AU - Aphecetche, L.

AU - Appelshäuser, H.

AU - Arcelli, S.

AU - Arnaldi, R.

AU - Arnold, O. W.

AU - Arsene, I. C.

AU - Arslandok, M.

AU - Audurier, B.

AU - Augustinus, A.

AU - Averbeck, R.

AU - Bock, F.

AU - Read, K. F.

AU - Schmidt, N. V.

PY - 2019/2/21

Y1 - 2019/2/21

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AB - Measurements of inclusive and direct photon production at midrapidity in pp collisions at s=2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.47 GeV/c is at least one σ above unity and consistent with expectations from next-to-leading order pQCD calculations.

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JO - Physical Review C

JF - Physical Review C

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ER -

Direct photon production at low transverse momentum in proton-proton collisions at s =2.76 and 8 TeV

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