Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions.

The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3  GeV/c) direct-photon yields from Au+Au collisions at sqrt[s_{NN}]=39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrt[s_{NN}]=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1  GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5  GeV/c), but when results from different collision energies are compared, an additional sqrt[s_{NN}]-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.

M. K. Lee | K. O. Eyser | F. Fleuret | D. Kim | Y. Kim | K. Nakamura | R. Hollis | A. Mignerey | R. Nouicer | R. Pak | M. Patel | J. Hanks | M. Deaton | A. Kiyomichi | A. Angerami | A. Basye | F. Bauer | Z. Citron | M. Donadelli | F. Ellinghaus | P. Gallus | N. Grau | J. Jia | O. Jinnouchi | S. Kaneti | M. Leite | B. Lenzi | A. Milov | J. Moss | T. Nakamura | T. Ichihara | X. Jiang | J. Kang | J. Kang | H. Kim | S. Lee | Y. Onuki | D. Isenhower | J. Hill | D. Perepelitsa | M. Proissl | V. Khachatryan | T. Dahms | R. Choudhury | D. Dutta | A. Mohanty | B. Hong | S. Park | S. Afanasiev | M. Nguyen | J. Alexander | M. Hohlmann | G. Kunde | M. Issah | C. Maguire | M. Finger | S. Greene | A. Malakhov | D. d’Enterria | K. Lee | B. Lee | A. Kiss | K. Dehmelt | T. Fusayasu | A. Oskarsson | H. Moon | G. Baksay | L. Baksay | Y. Ikeda | R. Ichimiya | M. Csanád | T. Csörgő | T. Novák | B. Park | M. Reuter | Y. Leung | M. Germain | M. Heffner | J. Klay | J. Mitchell | B. Norman | J. Bhom | C. Ogilvie | J. Peng | J. Jin | D. Kotchetkov | G. Grim | O. Chvála | J. Haggerty | S. Lökös | J. Frantz | R. Granier de Cassagnac | S. Gadrat | V. Papavassiliou | D. Mcglinchey | R. Hayano | S. Chernichenko | K. Read | E. Hartouni | J. Kamin | M. Nagy | C. Aidala | J. Durham | I. Ravinovich | O. Drapier | J. Imrek | A. Iordanova | J. Nagle | K. Hill | B. Cole | Y. Efremenko | N. Apadula | L. Aphecetche | R. Averbeck | A. Baldisseri | Y. Berdnikov | D. Blau | H. Borel | H. Buesching | T. Chujo | B. Espagnon | S. Fokin | T. Gunji | H. Hamagaki | M. Inaba | B. Jacak | A. Kazantsev | A. Khanzadeev | C. Klein-boesing | F. Krizek | V. Manko | Y. Miake | C. Nattrass | N. Novitzky | A. Nyanin | J. Nystrand | H. Pei | J. Rak | A. Rakotozafindrabe | K. Reygers | V. Riabov | S. Kim | J. Newby | A. Enokizono | A. Glenn | H. Pereira | T. Moukhanova | J. Hamblen | H. Delagrange | R. Akimoto | T. Awes | D. Peressounko | K. Ozawa | J. Charvet | I. Otterlund | D. Kim | P. Constantin | Y. Hori | T. Horaguchi | A. Adare | V. Canoa Roman | Z. Conesa del Valle | K. Das | S. Esumi | I. Garishvili | M. Kim | R. Belmont | M. Connors | A. Morreale | W. J. Park | H. Masui | P. Garg | E. Aschenauer | K. Barish | M. Daugherity | J. Drachenberg | D. Kincses | L. Kochenda | R. Lacey | J. Lee | X. Li | H. Liu | S. Mioduszewski | T. Niida | S. Choi | M. Gonin | J. Boissevain | G. Mitsuka | E. Kim | D. Bucher | M. Comets | J. Gosset | J. Osborn | A. Frawley | O. Dietzsch | S. Aronson | V. Kochetkov | P. Kroon | M. Leitgab | Y. Miyachi | Z. Fraenkel | S. Rembeczki | T. Hachiya | V. Pantuev | J. Park | A. Berdnikov | A. Drees | A. Franz | I. Ojha | D. S. Brown | C. Chi | S. Bathe | L. Guo | K. Drees | A. Durum | K. Karatsu | I. Park | S. Nagamiya | M. Purschke | E. Atomssa | M. Harvey | A. Bazilevsky | T. Liska | M. Malik | T. Isobe | Y. Kwon | K. Hasuko | S. Pate | J. Kikuchi | M. Kawashima | K. Nagashima | Y. Cobigo | B. Kim | C. Chen | N. Ajitanand | Y. Akiba | K. Aoki | H. Asano | B. Azmoun | V. Babintsev | M. Bai | B. Bannier | B. Bassalleck | V. Baublis | S. Baumgart | J. Bok | K. Boyle | M. Brooks | J. Bryslawskyj | V. Bumazhnov | S. Butsyk | J. Chai | I. Choi | P. Christiansen | V. Cianciolo | L. D'Orazio | S. Dairaku | A. Datta | G. David | A. Denisov | E. Desmond | L. Ding | A. Dion | J. Do | T. Engelmore | B. Fadem | N. Feege | D. Fields | Y. Fukao | K. Gainey | C. Gal | A. Garishvili | H. Ge | X. Gong | K. Hahn | S. Hasegawa | T. Haseler | K. Hashimoto | X. He | T. Hemmick | T. Hester | J. Huang | K. Imai | A. Isupov | B. Johnson | K. Joo | D. Jouan | D. Jumper | B. H. Kang | D. Kawall | K. Kijima | E. Kim | K. Kim | Y. Kim | E. Kistenev | J. Klatsky | D. Kleinjan | P. Kline | Y. Komatsu | B. Komkov | J. Koster | D. Kotov | M. Kurosawa | Y. Lai | J. Lajoie | A. Lebedev | K. Lee | M. Leitch | B. Lewis | S. Lim | A. Litvinenko | M. Liu | B. Love | D. Lynch | Y. Makdisi | M. Makek | A. Manion | E. Mannel | S. Masumoto | M. McCumber | P. McGaughey | C. McKinney | M. Mendoza | B. Meredith | T. Mibe | D. Mishra | S. Miyasaka | T. Moon | D. Morrison | S. Motschwiller | T. Murakami | J. Murata | A. Mwai | T. Nagae | I. Nakagawa | Y. Nakamiya | K. Nakano | A. Nederlof | M. Nihashi | E. O’Brien | K. Okada | L. Patel | V. Peresedov | R. Petti | C. Pinkenburg | R. Pisani | H. Qu | D. Reynolds | Y. Riabov | E. Richardson | M. Alfred | Y. Aramaki | H. En’yo | Y. Goto | K. Homma | D. Ivanishchev | H. Al-Bataineh | J. Asai | P. Barnes | S. Batsouli | C. Baumann | S. Belikov | R. Bennett | A. Bickley | G. Bunce | C. M. Camacho | A. Caringi | B. Chang | W. Chang | M. Chiu | P. Chung | A. Churyn | I. Danchev | M. Dayananda | A. Deshpande | K. V. Dharmawardane | A. Dubey | V. Dzhordzhadze | S. Edwards | K. Fujiwara | H. Gong | H. Gustafsson | R. Han | K. Haruna | E. Haslum | W. Holzmann | H. Iinuma | M. Ishihara | Y. Iwanaga | T. Jones | F. Kajihara | S. Kametani | N. Kamihara | J. Kapustinsky | M. Kasai | T. Kempel | A. Kim | E. Kinney | K. Kiriluk | M. Konno | A. Kozlov | A. Kravitz | M. J. Kweon | G. Kyle | D. Layton | D. Lee | T. Lee | P. Lichtenwalner | P. Liebing | Y. Mao | F. Matathias | N. Means | K. Miki | M. Mishra | Y. Morino | D. Mukhopadhyay | M. Naglis | S. Nam | C. Oakley | S. Oda | M. Oka | M. Ouchida | A. Palounek | A. Purwar | Y. Le Bornec | J. Heuser | B. Forestier | M. Mitrovski | T. Danley | W. Fan | M. Grosse Perdekamp | A. Hodges | Z. Ji | B. Kurgyis | N. Lewis | T. Majoros | S. Morrow | J. Orjuela Koop | W. Peng | C. PerezLara | P. Radzevich | I. Ravinovich | D. Richford | A. Al-Jamel | R. Armendariz | J. Burward-Hoy | S. Fung | L. Isenhower | S. Kelly | M. C. McCain | G. Mishra | K. Kurita | Sarah Campbell | J. Chiba | C. Cleven | J. Egdemir | W. Emam | A. Hadj Henni | C. Haegemann | H. Harada | H. Hiejima | R. Hobbs | Y. Inoue | M. Kaneta | H. Kanou | A. Král | J. Kubart | N. Kurihara | L. Mašek | P. Mikes | T. E. Miller | Y. Nagata | O. Omiwade | D. Pal | H. Al-Ta’ani | P. Castera | S. Lee | L. A. Linden Levy | N. Hotvedt | S. Mohapatra | M. Boer | D. Mihalik | A. Bagoly | S. Leckey | H. Lim | M. T. Bjørndal | F. Gastineau | M. Hagiwara | M. Holmes | M. Hur | T. Kawagishi | Y. Kim | H. Ohnishi | D. Hornback | M. Javani | B. S. Chang | S. Huang | J. Choi | C. Camacho | C. Kim | I. Park | W. Fan | S. Choi | T. Novak | S. Choi | B. Lee | S. Lim | B. Kang | M. Kweon | W. Peng | K. Hahn | J. Kang | M. Nguyen | Y. Miyachi | D. Dutta | D. Kim | M. Kim | S. Greene | B. Kang | I. Nakagawa | J. Jia | H. Moon | H. Qu | X. Li | D. Kim | A. Mignerey | J. Alexander | K. Aoki | T. Novak | J. Hill | D. Morrison | S. Pate | A. Angerami | K. Nakamura | D. Brown | E. Kim | A. Morreale | M. Chiu | S. Hasegawa | K. Imai | J. Mitchell | E. O'brien | A. Kozlov | T. E. Miller | T. Jones

[1]  A. Snigirev,et al.  Probing confinement by direct photons and dileptons , 2018, The European Physical Journal A.

[2]  Jr.,et al.  Low-momentum direct-photon measurement in Cu + Cu collisions at sNN=200GeV , 2018, Physical Review C.

[3]  J. D. Castaño-Yepes,et al.  Erratum: Prompt photon yield and elliptic flow from gluon fusion induced by magnetic fields in relativistic heavy-ion collisions [Phys. Rev. D 96 , 014023 (2017)] , 2017 .

[4]  G. S. Averichev,et al.  Direct virtual photon production in Au+Au collisions at sNN=200 GeV , 2017 .

[5]  Prompt photon yield and elliptic flow from gluon fusion induced by magnetic fields in relativistic heavy-ion collisions , 2017, 1704.02433.

[6]  K. Reygers,et al.  Parametric estimate of the relative photon yields from the glasma and the quark-gluon plasma in heavy-ion collisions , 2017, 1701.05064.

[7]  A. Ayala,et al.  Magnetic catalysis of a finite-size pion condensate , 2016, 1609.02595.

[8]  J. Rademacker,et al.  Review of Multibody Charm Analyses , 2016 .

[9]  M. G. Fleck,et al.  Direct photon production in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$ = 2.76 TeV , 2015, 1509.07324.

[10]  Jr.,et al.  Azimuthally anisotropic emission of low-momentum direct photons in Au + Au collisions at sNN =200 GeV , 2015, 1509.07758.

[11]  S. Jeon,et al.  Production of photons in relativistic heavy-ion collisions , 2015, 1509.06738.

[12]  M. K. Lee,et al.  Transverse energy production and charged-particle multiplicity at midrapidity in various systems from $\sqrt{s_{NN}}=7.7$ to 200 GeV , 2015, 1509.06727.

[13]  S. Jeon,et al.  Thermal Photon Radiation in High Multiplicity p+Pb Collisions at the Large Hadron Collider. , 2015, Physical review letters.

[14]  L. Mclerran,et al.  A tale of tails: Photon rates and flow in ultra-relativistic heavy ion collisions , 2015, 1504.07223.

[15]  W. Cassing,et al.  Effective QCD and transport description of dilepton and photon production in heavy-ion collisions and elementary processes , 2015, 1512.08126.

[16]  J. G. Contreras,et al.  Direct photon production in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$ = 2.76 TeV , 2015, 1509.07324.

[17]  W. Cassing,et al.  Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions , 2015, 1504.05699.

[18]  Matthew Heffernan,et al.  Universal parametrization of thermal photon rates in hadronic matter , 2014, 1411.7012.

[19]  M. He,et al.  Pseudo-critical enhancement of thermal photons in relativistic heavy-ion collisions? , 2014, 1404.2846.

[20]  E. Bratkovskaya.  Phenomenology of photon and dilepton production in relativistic nuclear collisions , 2014, 1408.3674.

[21]  M. K. Lee,et al.  Transverse energy (ET) distributions at mid-rapidity in p+p, d+Au and Au+Au collisions at sNN=200 GeV and implications for particle production models☆ , 2014, 1408.0397.

[22]  Jr.,et al.  Centrality dependence of low-momentum direct-photon production in Au+Au collisions at sNN=200 GeV , 2014, 1405.3940.

[23]  L. Mclerran,et al.  The Glasma, photons and the implications of anisotropy , 2014, 1403.7462.

[24]  A. Monnai.  Thermal photon v 2 with slow quark chemical equilibration , 2014, 1403.4225.

[25]  I. Zahed,et al.  Electromagnetic Radiation in Hot QCD Matter: Rates, Electric Conductivity, Flavor Susceptibility and Diffusion , 2014, 1403.1632.

[26]  D. Kharzeev,et al.  Magneto-sonoluminescence and its signatures in photon and dilepton production in relativistic heavy ion collisions , 2014, 1402.2286.

[27]  W. Cassing,et al.  Centrality dependence of the direct photon yield and elliptic flow in heavy-ion collisions at sqrt(s)=200 GeV , 2013, 1311.0279.

[28]  B. Muller,et al.  Elliptic flow from thermal photons with magnetic field in holography , 2013, 1308.6568.

[29]  U. Heinz,et al.  Thermal photons as a quark-gluon plasma thermometer reexamined , 2013, 1308.2440.

[30]  F. Fleuret,et al.  Neutral pion production with respect to centrality and reaction plane in Au plus Au collisions at root S-NN=200 GeV , 2012, 1208.2254.

[31]  A. Leonidov,et al.  Production of photons and dileptons in the Glasma , 2012, 1202.3679.

[32]  D. Lohner.  Measurement of Direct-Photon Elliptic Flow in Pb-Pb Collisions at = 2.76 TeV , 2012, 1212.3995.

[33]  D. Kharzeev,et al.  Conformal anomaly as a source of soft photons in heavy ion collisions. , 2012, Physical review letters.

[34]  K. O. Eyser,et al.  Evolution of π(0) suppression in Au+Au collisions from √(s(NN))=39 to 200 GeV. , 2012, Physical review letters.

[35]  M. Dion,et al.  Viscous photons in relativistic heavy ion collisions , 2011, 1109.4405.

[36]  R. Rapp,et al.  Thermal photons and collective flow at energies available at the BNL Relativistic Heavy-Ion Collider , 2011, 1108.2131.

[37]  F. Fleuret,et al.  Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions , 2011, 1105.4126.

[38]  Z. Citron,et al.  Design, construction, operation and performance of a Hadron Blind Detector for the PHENIX experiment , 2011, 1103.4277.

[39]  Y. Akiba.  Enhanced production of direct photons in Au+Au collisions at √s NN =200 GeV and implications for the initial temperature , 2010 .

[40]  I. Zahed,et al.  Thermal photons from heavy ion collisions: A spectral function approach , 2009, 0911.2426.

[41]  E. al.,et al.  Enhanced Production of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV and Implications for the Initial Temperature , 2008, 0804.4168.

[42]  M. K. Lee,et al.  Enhanced Production of Direct Photons in Au þ Au Collisions at ffiffiffiffiffiffiffiffi sNN p 1⁄4 200 GeV and Implications for the Initial Temperature , 2010 .

[43]  S. Kiselev,et al.  Direct photon production from hadronic sources in high-energy heavy-ion collisions , 2008, 0806.3465.

[44]  Haijiang Gong.  Measurement of direct photons in ultra-relativistic Au+Au collisions , 2008 .

[45]  R. Rapp,et al.  Electromagnetic probes at RHIC-II , 2006, nucl-ex/0611009.

[46]  E. Pilon,et al.  Recent critical study of photon production in hadronic collisions , 2006, hep-ph/0602133.

[47]  P. Stankus.  Direct Photon Production in Relativistic Heavy-Ion Collisions , 2005 .

[48]  P. Kulinich,et al.  Interferometry of direct photons in central 208Pb + 208Pb collisions at 158A GeV. , 2004, Physical review letters.

[49]  R. Rapp,et al.  Hadronic production of thermal photons , 2003, hep-ph/0308085.

[50]  M. A. Kelley,et al.  PHENIX central arm tracking detectors , 2003 .

[51]  C. L. Britton,et al.  PHENIX inner detectors , 2003 .

[52]  L. W. Wright,et al.  PHENIX central arm particle ID detectors , 2003 .

[53]  Nilsson,et al.  Observation of direct photons in central 158A GeV (208)P(208)b+Pb collisions , 2000, Physical review letters.

[54]  E. al.,et al.  Observation of Direct Photons in Central 158 A GeV 208Pb+208Pb Collisions , 2000, nucl-ex/0006008.

[55]  Hayes,et al.  Review of Particle Physics. , 1996, Physical review. D, Particles and fields.

[56]  K. J. Powell,et al.  Direct Photon Production at the {CERN} {ISR} , 1989 .

[57]  B. Blumenfeld,et al.  Search for direct single-photon production at large pT in photon-proton collisions at √s = 62.4 GeV , 1980 .

[58]  H. Fritzsch,et al.  Measuring QCD compton effects , 1977 .

[59]  E. L. Feinberg.  Direct production of photons and dileptons in thermodynamical models of multiple hadron production , 1976, Il Nuovo Cimento A.

[60]  D. Levi,et al.  Perturbative approach to some one-dimensional many-body problems. I: Discussion of the Rayleigh-Schrödinger and Brillouin-Wigner series for the Sutherland model , 1976 .