Detailed measurement of thee+e−pair continuum inp+pandAu+Aucollisions atsNN=200GeV and implications for direct photon production

A Adare,M J Tannenbaum,I D Ojha,K Ozawa,D Sharma,K Dehmelt,O Drapier,B V Jacak,H Gong,J Rak,P D Barnes,V Singh,B Lenzi,F Kajihara,M Hohlmann,K Miki,S Nagamiya,T Tabaru,H Hiejima,M Slunečka,I Nakagawa,A Milov,J Egdemir,A Král,S H Aronson,E Kistenev,K Das,T Fusayasu,L Kochenda,K Reygers,G R Young,H Okada,R Lacey,B Azmoun,P J Kroon,T Shohjoh,Y Goto,Y Le Bornec,T C Awes,N Grau,T Liška,D Lynch,K S Sim,K N Barish,H Qu,A Khanzadeev,N Willis,H Buesching,C L Silva,E O’Brien,H Torii,C Pinkenburg,A K Dubey,X R Wang,A Hadj Henni,E Stenlund,M Issah,M Virius,S Afanasiev,D Walker,J Seele,S Bathe,L Isenhower,A Baldisseri,D P Morrison,M Rosati,R Bennett,D Yu Peressounko,I Tserruya,W C Smith,B Love,S Mioduszewski,M Finger,J Kamin,R Han,K O Eyser,Y V Efremenko,E M Takagui,M Gonin,V Dzhordzhadze,D Bucher,I V Sourikova,D E Fields,A Taketani,M J Kweon,G Baksay,R Hobbs,O Dietzsch,J Jia,F Ellinghaus,M C Mccain,E Vznuzdaev,X He,V Babintsev,D Hornback,T Nakamura,K F Read,M G Hur,S Takagi,E P Hartouni,D H Kim,J E Frantz,J Park,W Xie,K Shoji,K Hasuko,J G Boissevain,M Mitrovski,G C Mishra,Y Fukao,T K Hemmick,D Silvermyr,A Franz,I Ravinovich,P Tarján,A Isupov,S Kelly,G S Kyle,A K Purwar,M Chiu,Y Nakamiya,A Bazilevsky,S Gadrat,A Lebedev,L Baksay,O O Omiwade,J Asai,M Nguyen,A Glenn,B Hong,J G Lajoie,C P Singh,P Chung,R S Towell,D Winter,M J Leitch,L Mašek,K Haruna,A Kravitz,H.-Å Gustafsson,Y Nagata,D D’Enterria,I Otterlund,S Rembeczki,V Papavassiliou,M A L Leite,V Semenov,J Sziklai,H Al-Bataineh,G Roche,J Tojo,K Nakano,T E Miller,X Li,F Bauer,A Malakhov,T Chujo,T Dahms,J M Burward-Hoy,M Kaneta,E J Desmond,L Zolin,R P Pisani,C L Woody,P W Stankus,J Nystrand,J M Heuser,A Rakotozafindrabe,M Grosse Perdekamp,T Hachiya,A Toia,A Soldatov,T Sakaguchi,I Younus,V Kochetkov,B M Johnson,S Kametani,I E Yushmanov,E Kim,A Kozlov,Y Watanabe,S Batsouli,T Hester,S K Tuli,H Borel,S Sawada,C Vale,C A Ogilvie,C Silvestre,M Donadelli,B Forestier,S Yokkaichi,A Kiyomichi,J S Haggerty,M B Deaton,C Zhang,M Shimomura,M Togawa,K Shigaki,M X Liu,A Drees,K Imai,J H Kang,Y Riabov,B Espagnon,R Seto,M Wysocki,J L Drachenberg,E T Atomssa,A Deshpande,W S Emam,M L Brooks,H W Van Hecke,M L Purschke,S Butsyk,G J Kunde,S Sakai,T Sugitate,M Germain,M Oka,K Okada,D Kotchetkov,T L Thomas,T Kawagishi,T V Moukhanova,J Chiba,A Shevel,J P Sullivan,C R Cleven,J Velkovska,M Ouchida,Y Tanaka,Y Tsuchimoto,L Tomášek,D J Kim,J Ying,M T Bjorndal,R A Soltz,H Pei,Y.-S Kim,H Hamagaki,N Kamihara,R Nouicer,D M Lee,F Gastineau,K Fujiwara,M Mccumber,J Newby,S Leckey,M Holmes,A Taranenko,M Konno,R Averbeck,G David,V Baublis,C Haegemann,V Vrba,H Masui,T Ichihara,A Al-Jamel,R Seidl,A Litvinenko,S Skutnik,M D Malik,P Rukoyatkin,D Mukhopadhyay,Y Kwon,A Yanovich,H Sakata,E Haslum,A Denisov,J Alexander,H En’Yo,S Zhou,I Shein,A Durum,A Ster,J M Moss,M Mishra,O Jinnouchi,T Isobe,M Ishihara,V Pantuev,Y Akiba,K Homma,D Isenhower,W A Zajc,M Heffner,Y I Makdisi,K Boyle,R Hayano,M Reuter,Y Miake,T Lee,F Matathias,O Zaudtke,H Lim,Z Yasin,J L Nagle,H Delagrange,B Komkov,A Churyn,V Riabov,V Bumazhnov,K Tanida,A Enokizono,T Gunji,J Jin,A V Kazantsev,Y Inoue,D S Brown,V Cianciolo,V Peresedov,Y Mao,V L Rykov,R Pak,J Zimányi,D Pal,N Kurihara,W Holzmann,W E Sondheim,M Inaba,Y Cobigo,M Harvey,M P Comets,S P Stoll,A Romana,J Kubart,W J Park,P L Mcgaughey,N N Ajitanand,K S Joo,S F Pate,M Naglis,A D Frawley,C Suire,S Esumi,B Sahlmueller,I J Choi,H Pereira,A A Bickley,T Horaguchi,K Kurita,H Tydesjö,V Samsonov,S Campbell,P Mikeš,P Rosnet,G Bunce,L Aphecetche,J Murata,F Fleuret,I Garishvili,B Bassalleck,N Saito,P Constantin,A Dion,T K Shea,A Morreale,D Jouan,Y Berdnikov,E Kinney,X H Li,D Kawall,S S Ryu,M Csanád,N Tyurin,M K Lee,F Staley,H Valle,J T Mitchell,Z Fraenkel,S Chernichenko,R Granier De Cassagnac,J C Hill,M Stepanov,J Gösset ,J S Chai ,S Fokin ,B Chang ,J L Charvet ,S S.e Rosendahl ,Yue Shi Lai ,Christian Klein-Boesing ,Y Yamaguchi ,H Ohnìshì ,R Vértesi ,Masayuki Hagiwara ,А Виноградов ,R Arméndariz ,Susumu Sato ,S Oda ,S White ,A P.t Palounek ,B Cole ,J L Klay ,С Беликов ,B Norman ,J P Wessels ,C A Aidala ,A M Sickles ,Hideaki Kano ,S P Sørensen ,V N Tram ,V Manko ,Á Kiss ,Mathias Wagner ,T Csörgõ ,Hiroyuki Harada ,C Maguire ,S Y Fung ,C Y ,J C Peng ,Jun Kikuchi ,Kazuhiro Tanaka ,H Sato ,A Öskarsson ,A Nyanin ,T A Shibata ,Kazuo Aoki ,S Greene

doi:10.1103/physrevc.81.034911

Abstract

PHENIX has measured the e+e− pair continuum in sNN=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e+e− yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate-mass region, between the masses of the ϕ and the J/ψ meson, the yield is consistent with expectations from correlated cc̄ production, although other mechanisms are not ruled out. In the low-mass region, below the ϕ, the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7±0.4stat±1.5syst±0.9model. At low mass (mee<0.3 GeV/c2) and high pT (1<pT<5 GeV/c) an enhanced e+e− pair yield is observed that is consistent with production of virtual direct photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in pT, with inverse slope T=221±19stat±19syst MeV. Hydrodynamical models with initial temperatures ranging from Tinit≃300–600 MeV at times of 0.6–0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low pT<1 GeV/c the low-mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T≃100 MeV. Theoretical models underpredict the low-mass, low-pT enhancement.43 MoreReceived 1 December 2009DOI:https://doi.org/10.1103/PhysRevC.81.034911©2010 American Physical Society

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