Photon-hadron jet correlations in p plus p and Au plus Au collisions at s(NN)=200 GeV

Adare A, Afanasiev S, Aidala C, Ajitanand NN, Akiba Y, Al-Bataineh H, Alexander J, Al-Jamel A, Aoki K, Aphecetche L, Armendariz R, Aronson SH, Asai J, Atomssa ET, Averbeck R, Awes TC, Azmoun B, Babintsev V, Bai M, Baksay G, Baksay L, Baldisseri A, Barish KN, Barnes PD, Bassalleck B, Basye AT, Bathe S, Batsouli S, Baublis V, Bauer F, Baumann C, Bazilevsky A, Belikov S, Bennett R, Berdnikov A, Berdnikov Y, Bickley AA, Bjorndal MT, Boissevain JG, Borel H, Boyle K, Brooks ML, Brown DS, Bucher D, Buesching H, Bumazhnov V, Bunce G, Burward-Hoy JM, Butsyk S, Camacho CM, Campbell S, Chai JS, Chang BS, Chang WC, Charvet JL, Chen CH, Chernichenko S, Chiba J, Chi CY, Chiu M, Choi IJ, Choudhury RK, Chujo T, Chung P, Churyn A, Cianciolo V, Citron Z, Cleven CR, Cobigo Y, Cole BA, Comets MP, Connors M, Constantin P, Csanad M, Csorgo T, Dahms T, Dairaku S, Das K, David G, Deaton MB, Dehmelt K, Delagrange H, Denisov A, d'Enterria D, Deshpande A, Desmond EJ, Dietzsch O, Dion A, Donadelli M, Drachenberg JL, Drapier O, Drees A, Drees KA, Dubey AK, Durum A, Dutta D, Dzhordzhadze V, Efremenko YV, Egdemir J, Ellinghaus F, Emam WS, Engelmore T, Enokizono A, En'yo H, Espagnon B, Esumi S, Eyser KO, Fadem B, Fields DE, Finger M, Finger M, Fleuret F, Fokin SL, Forestier B, Fraenkel Z, Frantz JE, Franz A, Frawley AD, Fujiwara K, Fukao Y, Fung SY, Fusayasu T, Gadrat S, Garishvili I, Gastineau F, Germain M, Glenn A, Gong H, Gonin M, Gosset J, Goto Y, de Cassagnac RG, Grau N, Greene SV, Perdekamp MG, Gunji T, Gustafsson HA, Hachiya T, Henni AH, Haegemann C, Haggerty JS, Hagiwara MN, Hamagaki H, Han R, Harada H, Hartouni EP, Haruna K, Harvey M, Haslum E, Hasuko K, Hayano R, Heffner M, Hemmick TK, Hester T, Heuser JM, He X, Hiejima H, Hill JC, Hobbs R, Hohlmann M, Holmes M, Holzmann W, Homma K, Hong B, Horaguchi T, Hornback D, Huang S, Hur MG, Ichihara T, Ichimiya R, Ikeda Y, Imai K, Imrek J, Inaba M, Inoue Y, Isenhower D, Isenhower L, Ishihara M, Isobe T, Issah M, Isupov A, Ivanischev D, Jacak BV, Jia J, Jin J, Jinnouchi O, Johnson BM, Joo KS, Jouan D, Kajihara F, Kametani S, Kamihara N, Kamin J, Kaneta M, Kang JH, Kanou H, Kapustinsky J, Kawagishi T, Kawall D, Kazantsev AV, Kelly S, Kempel T, Khanzadeev A, Kijima KM, Kikuchi J, Kim BI, Kim DH, Kim DJ, Kim E, Kim SH, Kim YS, Kinney E, Kiriluk K, Kiss A, Kistenev E, Kiyomichi A, Klay J, Klein-Boesing C, Kochenda L, Kochetkov V, Komkov B, Konno M, Koster J, Kotchetkov D, Kozlov A, Kral A, Kravitz A, Kroon PJ, Kubart J, Kunde GJ, Kurihara N, Kurita K, Kurosawa M, Kweon MJ, Kwon Y, Kyle GS, Lacey R, Lai YS, Lai YS, Lajoie JG, Layton D, Lebedev A, Le Bornec Y, Leckey S, Lee DM, Lee KB, Lee MK, Lee T, Leitch MJ, Leite MAL, Lenzi B, Liebing P, Lim H, Liska T, Litvinenko A, Liu H, Liu MX, Li X, Li XH, Love B, Lynch D, Maguire CF, Makdisi YI, Malakhov A, Malik MD, Manko VI, Mannel E, Mao Y, Masek L, Masui H, Matathias F, McCain MC, McCumber M, McGaughey PL, Means N, Meredith B, Miake Y, Mikes P, Miki K, Miller TE, Milov A, Mioduszewski S, Mishra GC, Mishra M, Mitchell JT, Mitrovski M, Mohanty AK, Morino Y, Morreale A, Morrison DP, Moss JM, Moukhanova TV, Mukhopadhyay D, Murata J, Nagamiya S, Nagata Y, Nagle JL, Naglis M, Nagy MI, Nakagawa I, Nakamiya Y, Nakamura T, Nakano K, Newby J, Nguyen M, Niita T, Norman BE, Nouicer R, Nyanin AS, Nystrand J, O'Brien E, Oda SX, Ogilvie CA, Ohnishi H, Ojha ID, Okada H, Okada K, Oka M, Omiwade OO, Onuki Y, Oskarsson A, Otterlund I, Ouchida M, Ozawa K, Pak R, Pal D, Palounek APT, Pantuev V, Papavassiliou V, Park J, Park WJ, Pate SF, Pei H, Peng JC, Pereira H, Peresedov V, Peressounko DY, Pinkenburg C, Pisani RP, Purschke ML, Purwar AK, Qu H, Rak J, Rakotozafindrabe A, Ravinovich I, Read KF, Rembeczki S, Reuter M, Reygers K, Riabov V, Riabov Y, Roach D, Roche G, Rolnick SD, Romana A, Rosati M, Rosendahl SSE, Rosnet P, Rukoyatkin P, Ruzicka P, Rykov VL, Ryu SS, Sahlmueller B, Saito N, Sakaguchi T, Sakai S, Sakashita K, Sakata H, Samsono

Abstract

We report the observation at the Relativistic Heavy Ion Collider of suppression of back-to-back correlations in the direct photon+jet channel in Au+Au relative to p+p collisions. Two-particle correlations of direct photon triggers with associated hadrons are obtained by statistical subtraction of the decay photon-hadron (gamma-h) background. The initial momentum of the away-side parton is tightly constrained, because the parton-photon pair exactly balance in momentum at leading order in perturbative quantum chromodynamics, making such correlations a powerful probe of the in-medium parton energy loss. The away-side nuclear suppression factor, I-AA, in central Au+Au collisions, is 0.32 +/- 0.12(stat)+/- 0.09(syst) for hadrons of 3 < p(T)(h)< 5 in coincidence with photons of 5 < p(T)(gamma)< 15 GeV/c. The suppression is comparable to that observed for high-p(T) single hadrons and dihadrons. The direct photon associated yields in p+p collisions scale approximately with the momentum balance, z(T)equivalent to p(T)(h)/p(T)(gamma), as expected for a measurement of the away-side parton fragmentation function. We compare to Au+Au collisions for which the momentum balance dependence of the nuclear modification should be sensitive to the path-length dependence of parton energy loss.