TY - JOUR
T1 - Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV
AU - Adam, J.
AU - Adamova, D.
AU - Aggarwal, M.M.
AU - Aglieri Rinella, G.
AU - Agnello, Maria
AU - Agrawal, N.
AU - Ahammed, Z.
AU - U. Ahn, S.
AU - Aiola, S.
AU - Akindinov, A.
AU - Alessandro, B.
AU - Alme, J.
AU - Alkin, A.
AU - Andrei, C.
AU - Bearden, Ian
AU - Bøggild, Hans
AU - Christensen, Christian Holm
AU - Gulbrandsen, Kristjan Herlache
AU - Gaardhøje, Jens Jørgen
AU - Dalsgaard, Hans Hjersing
AU - Nielsen, Børge Svane
AU - Hansen, Alexander Colliander
AU - Bilandzic, Ante
AU - Chojnacki, Marek
AU - Zaccolo, Valentina
AU - Zhou, You
AU - Bourjau, Christian Alexander
PY - 2016/3/10
Y1 - 2016/3/10
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.
U2 - 10.1016/j.physletb.2016.01.020
DO - 10.1016/j.physletb.2016.01.020
M3 - Journal article
SN - 0370-2693
VL - 754
SP - 235
EP - 248
JO - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology
JF - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology
ER -