Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV

J. Adam; D. Adamova; M.M. Aggarwal; G. Aglieri Rinella; Maria Agnello; N. Agrawal; Z. Ahammed; S. U. Ahn; S. Aiola; A. Akindinov; B. Alessandro; J. Alme; A. Alkin; C. Andrei; Ian Bearden; Hans Bøggild; Christian Holm Christensen; Kristjan Herlache Gulbrandsen; Jens Jørgen Gaardhøje; Hans Hjersing Dalsgaard; Børge Svane Nielsen; Alexander Colliander Hansen; Ante Bilandzic; Marek Chojnacki; Valentina Zaccolo; You Zhou; Christian Alexander Bourjau

doi:10.1016/j.physletb.2016.01.020

Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV

J. Adam, D. Adamova, M.M. Aggarwal, G. Aglieri Rinella, Maria Agnello, N. Agrawal, Z. Ahammed, S. U. Ahn, S. Aiola, A. Akindinov, B. Alessandro, J. Alme, A. Alkin, C. Andrei, Ian Bearden, Hans Bøggild, Christian Holm Christensen, Kristjan Herlache Gulbrandsen, Jens Jørgen Gaardhøje, Hans Hjersing DalsgaardBørge Svane Nielsen, Alexander Colliander Hansen, Ante Bilandzic, Marek Chojnacki, Valentina Zaccolo, You Zhou, Christian Alexander Bourjau

Experimental Particle Physics

135 Citations (Scopus)

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Abstract

Direct photon production at mid-rapidity in Pb–Pb collisions at s_NN=2.76 TeV was studied in the transverse momentum range 0.9<p_T<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 p_T≳5 GeV/c. Direct photon spectra down to p_T≈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<p_T<2.1 GeV/c is 2.6σ for the 0–20% class. The spectrum in this p_T range and centrality class can be described by an exponential with an inverse slope parameter of (297±12^stat±41^syst) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.

Original language	English
Journal	Physics Letters B
Volume	754
Pages (from-to)	235-248
ISSN	0370-2693
DOIs	https://doi.org/10.1016/j.physletb.2016.01.020
Publication status	Published - 10 Mar 2016

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1-s2.0-S0370269316000320-mainFinal published version, 2.13 MBLicence: CC BY

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Adam, J., Adamova, D., Aggarwal, M. M., Aglieri Rinella, G., Agnello, M., Agrawal, N., Ahammed, Z., U. Ahn, S., Aiola, S., Akindinov, A., Alessandro, B., Alme, J., Alkin, A., Andrei, C., Bearden, I., Bøggild, H., Christensen, C. H., Gulbrandsen, K. H., Gaardhøje, J. J., ... Bourjau, C. A. (2016). Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV. Physics Letters B, 754, 235-248. https://doi.org/10.1016/j.physletb.2016.01.020

Adam, J, Adamova, D, Aggarwal, MM, Aglieri Rinella, G, Agnello, M, Agrawal, N, Ahammed, Z, U. Ahn, S, Aiola, S, Akindinov, A, Alessandro, B, Alme, J, Alkin, A, Andrei, C, Bearden, I , Bøggild, H , Christensen, CH , Gulbrandsen, KH , Gaardhøje, JJ, Dalsgaard, HH, Nielsen, BS, Hansen, AC, Bilandzic, A, Chojnacki, M, Zaccolo, V, Zhou, Y & Bourjau, CA 2016, 'Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV', Physics Letters B, vol. 754, pp. 235-248. https://doi.org/10.1016/j.physletb.2016.01.020

@article{49b0d968214a41a39f8423324724c32d,

title = "Direct photon production in Pb-Pb collisions at root s(NN)=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 = "J. Adam and D. Adamova and M.M. Aggarwal and {Aglieri Rinella}, G. and Maria Agnello and N. Agrawal and Z. Ahammed and {U. Ahn}, S. and S. Aiola and A. Akindinov and B. Alessandro and J. Alme and A. Alkin and C. Andrei and Ian Bearden and Hans B{\o}ggild and Christensen, {Christian Holm} and Gulbrandsen, {Kristjan Herlache} and Gaardh{\o}je, {Jens J{\o}rgen} and Dalsgaard, {Hans Hjersing} and Nielsen, {B{\o}rge Svane} and Hansen, {Alexander Colliander} and Ante Bilandzic and Marek Chojnacki and Valentina Zaccolo and You Zhou and Bourjau, {Christian Alexander}",

year = "2016",

month = mar,

day = "10",

doi = "10.1016/j.physletb.2016.01.020",

language = "English",

volume = "754",

pages = "235--248",

journal = "Physics Letters B",

issn = "0370-2693",

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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

JF - Physics Letters B

ER -

Direct photon production in Pb-Pb collisions at root s(NN)=2.76 TeV

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