Probing gluon number density with electron-dijet correlations at EIC

AbstractWe propose a novel way of studying the gluon number density (the so-called Weizsäcker–Williams gluon distribution) using the planned Electron Ion Collider. Namely, with the help of the azimuthal correlations between the total transverse momentum of the dijet system and the scattered electron, we examine an interplay between the effect of the soft gluon emissions (the Sudakov form factor) and the gluon saturation effects. The kinematic cuts are chosen such that the dijet system is produced in the forward direction in the laboratory frame, which provides an upper bound on the probed longitudinal fractions of the hadron momentum carried by scattered gluons. Further cuts enable us to use the factorization formalism that directly involves the unpolarized Weizsäcker–Williams gluon distribution. We find this observable to be very sensitive to the soft gluon emission and moderately sensitive to the gluon saturation.

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The importance of kinematic twists and genuine saturation effects in dijet production at the Electron-Ion Collider

Journal of High Energy Physics ◽

10.1007/jhep09(2021)178 ◽

2021 ◽

Vol 2021 (9) ◽

Cited By ~ 1

Author(s):

Renaud Boussarie ◽

Heikki Mäntysaari ◽

Farid Salazar ◽

Björn Schenke

Keyword(s):

High Energy ◽

Color Glass ◽

High Energy Electron ◽

Dijet Production ◽

Transverse Momentum Dependent ◽

Azimuthal Correlations ◽

Power Corrections ◽

Momentum Imbalance ◽

Gluon Saturation ◽

Saturation Effects

Abstract We compute the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small x as a function of the relative momentum P⊥ and momentum imbalance k⊥ of the dijet system for different photon virtualities Q2, and study the elliptic and quadrangular anisotropies in the relative angle between P⊥ and k⊥. We review and extend the analysis in [1], which compared the results of the Color Glass Condensate (CGC) with those obtained using the transverse momentum dependent (TMD) framework. In particular, we include in our comparison the improved TMD (ITMD) framework, which resums kinematic power corrections of the ratio k⊥ over the hard scale Q⊥. By comparing ITMD and CGC results we are able to isolate genuine higher saturation contributions in the ratio Qs/Q⊥ which are resummed only in the CGC. These saturation contributions are in addition to those in the Weizsäcker-Williams gluon TMD that appear in powers of Qs/k⊥. We provide numerical estimates of these contributions for inclusive dijet production at the future Electron-Ion Collider, and identify kinematic windows where they can become relevant in the measurement of dijet and dihadron azimuthal correlations. We argue that such measurements will allow the detailed experimental study of both kinematic power corrections and genuine gluon saturation effects.

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Forward di-jet production in p+Pb collisions in the small-x improved TMD factorization framework

Journal of High Energy Physics ◽

10.1007/jhep12(2016)034 ◽

2016 ◽

Vol 2016 (12) ◽

Cited By ~ 10

Author(s):

A. van Hameren ◽

P. Kotko ◽

K. Kutak ◽

C. Marquet ◽

E. Petreska ◽

...

Keyword(s):

Hadron Collider ◽

Forward Direction ◽

Gluon Density ◽

Longitudinal Momentum ◽

Proton Proton ◽

Proton Collisions ◽

Azimuthal Correlations ◽

Small X ◽

Saturation Effects ◽

Proton Proton Collisions

Abstract We study the production of forward di-jets in proton-lead and proton-proton collisions at the Large Hadron Collider. Such configurations, with both jets produced in the forward direction, impose a dilute-dense asymmetry which allows to probe the gluon density of the lead or proton target at small longitudinal momentum fractions. Even though the jet momenta are always much bigger than the saturation scale of the target, Q s, the transverse momentum imbalance of the di-jet system may be either also much larger than Q s, or of the order Q s, implying that the small-x QCD dynamics involved is either linear or non-linear, respectively. The small-x improved TMD factorization framework deals with both situations in the same formalism. In the latter case, which corresponds to nearly back-to-back jets, we find that saturation effects induce a significant suppression of the forward di-jet azimuthal correlations in proton-lead versus proton-proton collisions.

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