NLO impact factor for inclusive photon+dijet production in e+A DIS at small x

Abstract

We compute the next-to-leading order (NLO) impact factor for inclusive photon +dijet production in electron-nucleus (e+A) deeply inelastic scattering (DIS) at small x. An important ingredient in our computation is the simple structure of "shock wave" fermion and gluon propagators. This allows one to employ standard momentum space Feynman diagram techniques for higher order computations in the Regge limit of fixed Q 2 Λ 2 QCD and x → 0. Our computations in the Color Glass Condensate (CGC) effective field theory include the resummation of all-twist power corrections Q 2 s /Q 2 , where Qs is the saturation scale in the nucleus. We discuss the structure of ultraviolet, collinear and soft divergences in the CGC, and extract the leading logs in x; the structure of the corresponding rapidity divergences gives a nontrivial first principles derivation of the JIMWLK renormalization group evolution equation for multiparton lightlike Wilson line correlators. Explicit expressions are given for the x-independent O(αs) contributions that constitute the NLO impact factor. These results, combined with extant results on NLO JIMWLK evolution, provide the ingredients to compute the inclusive photon + dijet cross-section at small x to O(α 3 s ln(x)). First results for the NLO impact factor in inclusive dijet production are recovered in the soft photon limit. A byproduct of our computation is the LO photon+ 3 jet (quark-antiquark-gluon) cross-section. CONTENTS * kaushik.roy.1@stonybrook.edu † raju@bnl.gov arXiv:1911.04530v2 [hep-ph] 3 Dec 2019 97 J. Proof of the sub-dominance of non-collinearly divergent contributions in the SCA 100References 100

Photoproduction of three jets in the CGC: gluon TMDs and dilute limit

“…Our calculation provides an important contribution towards establishing the phenomenology of forward particle production at low-x, in the line of [43,47,59]. In particular, recently there has been much interest in processes with photons in the final state as a clean probe for saturation effects [42,[60][61][62][63][64], and it can be noted that the cross section for the JHEP07(2020)143 photoproduction of two jets and a photon can very easily be adapted from the results of the present paper, with a simplified Wilson line structure.…”

HERA data and collinearly-improved BK dynamics

“…Derived via systematic approximations within perturbative QCD, the Colour Glass Condensate (CGC) effective theory [1][2][3][4][5] is a powerful framework for computing high-energy processes in the presence of nonlinear effects associated with high parton densities. There are intense ongoing efforts towards extending this effective theory to next-to-leading order (NLO) accuracy, as required by realistic applications to phenomenology [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. These efforts refer both to the Balitsky-JIMWLK equations [20][21][22][23][24][25][26], which govern the high-energy evolution of the scattering amplitudes, and to the impact factors, which represent cross-sections at relatively low energy.…”

Multigluon Correlations and Evidence of Saturation from Dijet Measurements at an Electron-Ion Collider

“…Based on results in [19], we expect the v 2 of the produced q-q pair presented here to be a good estimator of the observable dijet v 2 . It will also be important to include next-toleading order (NLO) corrections, both in small-x evolution equations: NLO BK [58][59][60][61] or NLO JIMWLK [62,63], and the NLO impact factor [64][65][66][67][68], and to consider the effects of soft gluon radiation of the final state jets that is not captured by the jet algorithm [8].…”