Probing gluon saturation with next-to-leading order photon production at central rapidities in proton-nucleus collisions

Benić, Sanjin and Fukushima, Kenji and Garcia-Montero, Oscar and Venugopalan, Raju (2017) Probing gluon saturation with next-to-leading order photon production at central rapidities in proton-nucleus collisions. Journal of High Energy Physics, 2017 (1). Art. No. 115-36. ISSN 1029-8479

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We compute the cross section for photons emitted from sea quarks in protonnucleus collisions at collider energies. The computation is performed within the dilute-dense kinematics of the Color Glass Condensate (CGC) effective field theory. Albeit the result obtained is formally at next-to-leading order in the CGC power counting, it provides the dominant contribution for central rapidities. We observe that the inclusive photon cross section is proportional to all-twist Wilson line correlators in the nucleus. These correlators also appear in quark-pair production; unlike the latter, photon production is insensitive to hadronization uncertainties and therefore more sensitive to multi-parton correlations in the gluon saturation regime of QCD. We demonstrate that k⊥ and collinear factorized expressions for inclusive photon production are obtained as leading twist approximations to our result. In particular, the collinearly factorized expression is directly sensitive to the nuclear gluon distribution at small x. Other results of interest include the realization of the Low-Burnett-Kroll soft photon theorem in the CGC framework and a comparative study of how the photon amplitude is obtained in Lorenz and light-cone gauges.

Item Type: Article
Keywords: heavy ion phenomenology, NLO computations
Date: 2017
Subjects: NATURAL SCIENCES > Physics
Additional Information: Open Access, © The Author(s) 2017. Article funded by SCOAP3 and licensed under CC BY 4.0. Received: October 8, 2016. Accepted: January 15, 2017. Published: January 26, 2017.
Divisions: Faculty of Science > Department of Physics
Publisher: Springer
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 14 Nov 2017 21:51
Last Modified: 14 Nov 2017 21:51

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