Direct photon production in Pb–Pb collisions at √sNN=2.76 TeV

ALICE Collaboration

Research output: Contribution to journalArticle

83 Citations (Scopus)

Abstract

Direct photon production at mid-rapidity in Pb–Pb collisions at sNN=2.76 TeV was studied in the transverse momentum range 0.9<pT<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e+e pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0–20%, 20–40%, and 40–80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT≳5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20–40% and 0–20% centrality classes. The significance of the direct photon signal for 0.9<pT<2.1 GeV/c is 2.6σ for the 0–20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12stat±41syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.

Original languageEnglish (US)
Pages (from-to)235-248
Number of pages14
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume754
DOIs
StatePublished - Mar 10 2016

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collisions
photons
transverse momentum
ionic collisions
calorimeters
quantum chromodynamics
slopes
electromagnetism
detectors

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics

Cite this

Direct photon production in Pb–Pb collisions at √sNN=2.76 TeV. / ALICE Collaboration.

In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol. 754, 10.03.2016, p. 235-248.

Research output: Contribution to journalArticle

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title = "Direct photon production in Pb–Pb collisions at √sNN=2.76 TeV",
abstract = "Direct photon production at mid-rapidity in Pb–Pb collisions at sNN=2.76 TeV was studied in the transverse momentum range 0.9T<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e+e− pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0–20{\%}, 20–40{\%}, and 40–80{\%} centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT≳5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20–40{\%} and 0–20{\%} centrality classes. The significance of the direct photon signal for 0.9T<2.1 GeV/c is 2.6σ for the 0–20{\%} class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12stat±41syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.",
author = "{ALICE Collaboration} and J. Adam and D. Adamov{\'a} 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 Alam, {S. N.} and D. Aleksandrov and B. Alessandro and D. Alexandre and {Alfaro Molina}, R. and A. Alici and A. Alkin and Almaraz, {J. R.M.} and J. Alme and T. Alt and S. Altinpinar and I. Altsybeev and {Alves Garcia Prado}, C. and C. Andrei and A. Andronic and V. Anguelov and J. Anielski and T. Antičić and F. Antinori and P. Antonioli 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 Awes, {T. C.} and Azmi, {M. D.} and A. Badal{\`a} and Baek, {Y. W.} and S. Bagnasco and R. Bailhache and R. Bala and A. Baldisseri and Cherney, {Michael G.} and Seger, {Janet E.}",
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T1 - Direct photon production in Pb–Pb collisions at √sNN=2.76 TeV

AU - ALICE Collaboration

AU - Adam, J.

AU - Adamová, D.

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 - Alam, S. N.

AU - Aleksandrov, D.

AU - Alessandro, B.

AU - Alexandre, D.

AU - Alfaro Molina, R.

AU - Alici, A.

AU - Alkin, A.

AU - Almaraz, J. R.M.

AU - Alme, J.

AU - Alt, T.

AU - Altinpinar, S.

AU - Altsybeev, I.

AU - Alves Garcia Prado, C.

AU - Andrei, C.

AU - Andronic, A.

AU - Anguelov, V.

AU - Anielski, J.

AU - Antičić, T.

AU - Antinori, F.

AU - Antonioli, P.

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 - Awes, T. C.

AU - Azmi, M. D.

AU - Badalà, A.

AU - Baek, Y. W.

AU - Bagnasco, S.

AU - Bailhache, R.

AU - Bala, R.

AU - Baldisseri, A.

AU - Cherney, Michael G.

AU - Seger, Janet E.

PY - 2016/3/10

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N2 - Direct photon production at mid-rapidity in Pb–Pb collisions at sNN=2.76 TeV was studied in the transverse momentum range 0.9T<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e+e− pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0–20%, 20–40%, and 40–80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT≳5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20–40% and 0–20% centrality classes. The significance of the direct photon signal for 0.9T<2.1 GeV/c is 2.6σ for the 0–20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12stat±41syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.

AB - Direct photon production at mid-rapidity in Pb–Pb collisions at sNN=2.76 TeV was studied in the transverse momentum range 0.9T<14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e+e− pair reconstructed in the central tracking system. The results of the two methods were combined and direct photon spectra were measured for the 0–20%, 20–40%, and 40–80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for pT≳5 GeV/c. Direct photon spectra down to pT≈1 GeV/c could be extracted for the 20–40% and 0–20% centrality classes. The significance of the direct photon signal for 0.9T<2.1 GeV/c is 2.6σ for the 0–20% class. The spectrum in this pT range and centrality class can be described by an exponential with an inverse slope parameter of (297±12stat±41syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.

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U2 - 10.1016/j.physletb.2016.01.020

DO - 10.1016/j.physletb.2016.01.020

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VL - 754

SP - 235

EP - 248

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

SN - 0370-2693

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