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

2021 ◽  
Vol 2021 (9) ◽  
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.

scholarly journals Comparison of improved TMD and CGC frameworks in forward quark dijet production

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Hirotsugu Fujii ◽  
Cyrille Marquet ◽  
Kazuhiro Watanabe
Keyword(s):  
Azimuthal Angle ◽  
High Energy ◽  
Color Glass ◽  
Dijet Production ◽  
Proton Proton ◽  
Saturation Scale ◽  
Wide Range ◽  
Factorization Formula ◽  
Leading Term ◽  
Multi Body

Abstract For studying small-x gluon saturation in forward dijet production in high-energy dilute-dense collisions, the improved TMD (ITMD) factorization formula was recently proposed. In the Color Glass Condensate (CGC) framework, it represents the leading term of an expansion in inverse powers of the hard scale. It contains the leading-twist TMD factorization formula relevant for small gluon’s transverse momentum kt, but also incorporates an all-order resummation of kinematical twists, resulting in a proper matching to high-energy factorization at large kt. In this paper, we evaluate the accuracy of the ITMD formula quantitatively, for the case of quark dijet production in high-energy proton-proton(p+p) and proton-nucleus (p+A) collisions at LHC energies. We do so by comparing the quark-antiquark azimuthal angle ∆ϕ distribution to that obtained with the CGC formula. For a dijet with each quark momentum pt much larger than the target saturation scale, Qs, the ITMD formula is a good approximation to the CGC formula in a wide range of azimuthal angle. It becomes less accurate as the jet pt’s are lowered, as expected, due to the presence of genuine higher-twists contributions in the CGC framework, which represent multi-body scattering effects absent in the ITMD formula. We find that, as the hard jet momenta are lowered, the accuracy of ITMD start by deteriorating at small angles, in the high-energy-factorization regime, while in the TMD regime near ∆ϕ = π, very low values of pt are needed to see differences between the CGC and the ITMD formula. In addition, the genuine twists corrections to ITMD become visible for higher values of pt in p + A collisions, compared to p+p collisions, signaling that they are enhanced by the target saturation scale.

scholarly journals GLUON SATURATION AND THE FROISSART BOUND: A SIMPLE APPROACH

2008 ◽  
Vol 23 (33) ◽  
pp. 2847-2857 ◽  
Author(s):  
F. CARVALHO ◽  
F. O. DURÃES ◽  
V. P. GONÇALVES ◽  
F. S. NAVARRA
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Simple Approach ◽  
Strong Interactions ◽  
Color Glass ◽  
Momentum Scale ◽  
Total Cross Sections ◽  
High Energies ◽  
Gluon Saturation ◽  
Very High

At very high energies we expect that the hadronic cross sections satisfy the Froissart bound, which is a well-established property of the strong interactions. In this energy regime we also expect the formation of the Color Glass Condensate, characterized by gluon saturation and a typical momentum scale: the saturation scale Qs. In this paper we show that if a saturation window exists between the nonperturbative and perturbative regimes of Quantum Chromodynamics (QCD), the total cross sections satisfy the Froissart bound. Furthermore, we show that our approach allows us to describe the high energy experimental data on [Formula: see text] total cross sections.

scholarly journals Gluon saturation effects on the color singlet J/ψ production in high energy dA and AA collisions

2012 ◽  
Vol 710 (1) ◽  
pp. 182-187 ◽  
Author(s):  
F. Dominguez ◽  
D.E. Kharzeev ◽  
E.M. Levin ◽  
A.H. Mueller ◽  
K. Tuchin
Keyword(s):  
High Energy ◽  
Color Singlet ◽  
Gluon Saturation ◽  
Saturation Effects ◽  
Aa Collisions

scholarly journals Inclusive prompt photon-jet correlations as a probe of gluon saturation in electron-nucleus scattering at small x

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Isobel Kolbe ◽  
Kaushik Roy ◽  
Farid Salazar ◽  
Björn Schenke ◽  
Raju Venugopalan
Keyword(s):  
Numerical Study ◽  
Empirical Test ◽  
Azimuthal Angle ◽  
Color Glass ◽  
Angle Distribution ◽  
Prompt Photon ◽  
Matrix Elements ◽  
Dijet Production ◽  
Saturation Scale ◽  
Gluon Saturation

Abstract We compute the differential cross-section for inclusive prompt photon+quark production in deeply inelastic scattering of electrons off nuclei at small x (e + A DIS) in the framework of the Color Glass Condensate effective field theory. The result is expressed as a convolution of the leading order (in the strong coupling αs) impact factor for the process and universal dipole matrix elements, in the limit of hard photon transverse momentum relative to the nuclear saturation scale Qs,A(x). We perform a numerical study of this process for the kinematics of the Electron-Ion Collider (EIC), exploring in particular the azimuthal angle correlations between the final state photon and quark. We observe a systematic suppression and broadening pattern of the back-to-back peak in the relative azimuthal angle distribution, as the saturation scale is increased by replacing proton targets with gold nuclei. Our results suggest that photon+jet final states in inclusive e + A DIS at high energies are in general a promising channel for exploring gluon saturation that is complementary to inclusive and diffractive dijet production. They also provide a sensitive empirical test of the universality of dipole matrix elements when compared to identical measurements in proton-nucleus collisions. However because photon+jet correlations at small x in EIC kinematics require jet reconstruction at small k⊥, it will be important to study their feasibility relative to photon-hadron correlations.

scholarly journals Probing gluon number density with electron-dijet correlations at EIC

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
A. van Hameren ◽  
P. Kotko ◽  
K. Kutak ◽  
S. Sapeta ◽  
E. Żarów
Keyword(s):  
Gluon Distribution ◽  
Forward Direction ◽  
Laboratory Frame ◽  
Soft Gluon ◽  
Number Density ◽  
Scattered Electron ◽  
Gluon Emission ◽  
Azimuthal Correlations ◽  
Gluon Saturation ◽  
Saturation Effects

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.

Sign in / Sign up

Export Citation Format

Share Document