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

J., Adam ; Christiansen, P. LU ; Ljunggren, H. ; Oskarsson, A. LU ; Richert, T. LU ; Silvermyr, D. LU orcid ; Søgaard, C. LU ; Stenlund, E. LU ; Vislavicius, V. LU and M., Zyzak (2016) In Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 754. p.235-248
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... (More)
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.
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organization
publishing date
type
Contribution to journal
publication status
published
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in
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
volume
754
pages
14 pages
publisher
Elsevier
external identifiers
  • scopus:85040813298
ISSN
0370-2693
DOI
10.1016/j.physletb.2016.01.020
language
English
LU publication?
yes
id
394773a6-cef9-499a-96ce-269c50b07adc
date added to LUP
2022-04-04 14:48:06
date last changed
2023-05-10 15:22:32
@article{394773a6-cef9-499a-96ce-269c50b07adc,
  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&lt;pT&lt;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&lt;pT&lt;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. <br/>}},
  author       = {{J., Adam and Christiansen, P. and Ljunggren, H. and Oskarsson, A. and Richert, T. and Silvermyr, D. and Søgaard, C. and Stenlund, E. and Vislavicius, V. and M., Zyzak}},
  issn         = {{0370-2693}},
  language     = {{eng}},
  pages        = {{235--248}},
  publisher    = {{Elsevier}},
  series       = {{Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics}},
  title        = {{Direct photon production in Pb–Pb collisions at √sNN=2.76 TeV}},
  url          = {{http://dx.doi.org/10.1016/j.physletb.2016.01.020}},
  doi          = {{10.1016/j.physletb.2016.01.020}},
  volume       = {{754}},
  year         = {{2016}},
}