High-ET isolated-photon plus jets production in pp collisions at √s = 8 TeV with the ATLAS detector

Aaboud, M; Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Abeloos, B; AbouZeid, O S; Abraham, N L; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adachi, S; Adamczyk, L; Adams, D L; Adelman, J; Adomeit, S; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albrand, S; Alconada Verzini, M J

High-ET isolated-photon plus jets production in pp collisions at √s = 8 TeV with the ATLAS detector

Journal Article

2017

Journal Title

Nuclear Physics, B

Link to Journal

https://dx.doi.org/10.1016/j.nuclphysb.2017.03.006

Department

Department of Physics

Faculty

Faculty of Science

Abstract

Available online at www.sciencedirect.com ScienceDirect Nuclear Physics B 918 (2017) 257–316 www.elsevier.com/locate/nuclphysb High-E T isolated-photon plus jets production in pp collisions at s = 8 TeV with the ATLAS detector .The ATLAS Collaboration Received 21 November 2016; received in revised form 3 March 2017; accepted 6 March 2017 Available online 11 March 2017 Editor: Valerie Gibson Abstract The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of- mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb −1 . Measurements of isolated-photon plus jets cross sections are presented as func- tions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system are presented. The pattern of QCD radiation around the photon and the leading jet is investigated by measuring jet production in an annular region cen- tred on each object; enhancements are observed around the leading jet with respect to the photon in the directions towards the beams. The experimental measurements are compared to several different theoretical calculations, and overall a good description of the data is found. © 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP 3 . 1. Introduction The production of prompt photons in association with jets in proton–proton collisions, pp → γ + jets + X, provides a testing ground for perturbative QCD (pQCD) with a hard colour- less probe less affected by hadronisation effects than jet production. The measurements of the angular correlations between the photon and the jets can be used to probe the dynamics of the hard-scattering process. Since the dominant production mechanism in pp collisions at the Large Hadron Collider (LHC) proceeds via the qg → qγ process, measurements of prompt-photon plus jet production are useful in constraining the gluon density in the proton [1,2]. These mea- E-mail address: atlas.publications@cern.ch. http://dx.doi.org/10.1016/j.nuclphysb.2017.03.006 0550-3213/© 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP 3 .