Theory Of Color Glass Condensate Research Articles

Geometrical scaling of direct photons in relativistic heavy ion and D+Au collisions

In this paper, we show that multiplicity spectra of direct photons in A+A and d+Au collisions at different centrality classes and different energies exhibit geometrical scaling, i.e., they depend on a specific combination of number of participants Npart, collisions energy W, and transverse momentum pT – called saturation scale – rather than on all these three variables separately. In particular, the dependence on the geometry of collisions encoded in the dependence on Npart is in agreement with the expectations based on the Color Glass Condensate theory.

Dijet production at EIC and interplay of Sudakov and saturation effects in Weizsacker-Williams TMD gluon distribution

We study production of dijets at the EIC using the small-x Improved Transverse Momentum Dependent factorization (ITMD), which is a framework based on the Color Glass Condensate theory. Dijet production in DIS is the simplest process directly coupled to the Weizsäcker-Williams TMD gluon distribution, which is the only small-x gluon distribution possessing the gluon number density interpretation. We study various observables sensitive to the interplay of the Sudakov effects and the nonlinear effects, in particular the azimuthal correlations between the jet system and the scattered electron.

Memory effect in Yang-Mills theory

We study the empirical realisation of the memory effect in Yang-Mills theory, especially in view of the classical vs. quantum nature of the theory. Gauge invariant analysis of memory in classical U(1) electrodynamics and its observation by total change of transverse momentum of a charge is reviewed. Gauge fixing leads to a determination of a gauge transformation at infinity. An example of Yang-Mills memory then is obtained by reinterpreting known results on interactions of a quark and a large high energy nucleus in the theory of Color Glass Condensate. The memory signal is again a kick in transverse momentum, but it is only obtained in quantum theory after fixing the gauge, after summing over an ensemble of classical processes.

Signature of gluon saturation in forward di-hadron correlations at the Large Hadron Collider

We argue that gluon saturation effects may be visible in Large Hadron Collider (LHC) data. We look at the centrality dependence of the away-side peak of two-particle correlations measured in p-Pb collisions, using both ALICE data at midrapidity, and LHCb data at forward rapidity. Once the collective flow-like signal measured at the near-side peak is removed from the correlation function, the centrality dependence of the away-side peak turns out to be much stronger in the forward region than at midrapidity. We argue that this is a very specific prediction of the saturation framework, and we compare LHCb data to a state-of-the-art calculation within the Color Glass Condensate theory.

TMD gluon distributions at small x in the CGC theory

In this paper, we review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small [Formula: see text] in the color glass condensate (CGC) effective theory. We discuss the origin of the nonuniversality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small [Formula: see text], and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the nonlinear small-[Formula: see text] evolution of gluon distributions.

CGC and initial state effects in Heavy Ion Collisions

A brief review of the phenomenological studies in the field of heavy ion collisions based on the Color Glass Condensate theory and, in particular, of those relying in the use of the BK equation including running coupling effects is presented.

Color Glass Condensate and glasma

In this talk, I review the Color Glass Condensate theory of gluon saturation, and its application to the early stages of heavy ion collisions.

The relationship between the soft and hard ridges

Two particle correlation measurements in relativistic heavy ion collisions show a 'ridge' of correlated particle pairs not seen in proton on proton collisions. The measured two-dimentional correlation landscape resembles a mountain ridge since correlated pairs are focused into a narrow regions of relative azimuthal angle, but can extend to a long range in relative pseudorapidity. Similar ridge structures are observed in correlations of particles associated with and without a jet trigger. Explanations, with and without a jet, are challenged to explain the long range pseudorapidity behavior of correlations where causality limits the influence of transport dynamics. Glasma initial conditions as predicted by the theory of Color Glass Condensate provide a and early stage correlation that naturally extends far in rapidity. We have previously shown that the soft ridge is a consequence of particles forming from an initial Glasma phase that experience a later stage transverse flow. We extend this work to study the ridge dependence on the pt of the correlated pairs and determine the relationship between the triggered and untriggered measurements.

On the Wess–Zumino term in high energy QCD

Recently, Kovner and Lublinsky proposed new small- x QCD evolution equations valid when the gluon density inside the target is low. The key element of their construction is the Wess–Zumino term which ensures the non-commutativity of valence charges. In this paper we clarify the origin and significance of this term by showing that it can be naturally incorporated in the effective theory of Color Glass Condensate. We also reexamine the renormalization group description in the high density (JIMWLK) regime.

Cronin effect and high-pTsuppression inpAcollisions

We review the predictions of the theory of Color Glass Condensate for gluon production cross section in p(d)A collisions. We demonstrate that at moderate energies, when the gluon production cross section can be calculated in the framework of McLerran-Venugopalan model, it has only partonic level Cronin effect in it. At higher energies/rapidities corresponding to smaller values of Bjorken x quantum evolution becomes important. The effect of quantum evolution at higher energies/rapidities is to introduce suppression of high-p_T gluons slightly decreasing the Cronin enhancement. At still higher energies/rapidities quantum evolution leads to suppression of produced gluons at all values of p_T.