Multi-particle production in proton-nucleus collisions in the Color Glass Condensate
Pedro Agostini, Tolga Altinoluk, Néstor Armesto
备注：
LaTeX, 39 pages, 10 figures
发表信息：
Agostini, P., Altinoluk, T. & Armesto, N. Multi-particle production in proton-nucleus collisions in the color glass condensate. Eur. Phys. J. C 81, 760 (2021)
We compute multi-gluon production in the Color Glass Condensate approach in dilute-dense collisions, p$A$, extending previous calculations up to four gluons. We include the contributions that are leading in the overlap area of the collision but keep all orders in the expansion in the number of colors. We develop a diagrammatic technique to write the numerous color contractions and exploit the symmetries to group the diagrams and simplify the expressions. To proceed further, we use the McLerran-Venugopalan and Golec-Biernat-Wüsthoff models for the projectile and target averages, respectively. We use a form of the Lipatov vertices that leads to the Wigner function approach for the projectile previously employed, that we generalise to take into account quantum correlations in the projectile wave function. We provide analytic expressions for integrated and differential two gluon cumulants and show a smooth dependence on the parameters defining the projectile and target Wigner function and dipole, respectively. For four gluon correlations we find that the second order four particle cumulant is negative, so a sensible second Fourier azimuthal coefficient can be defined. The effect of correlations in the projectile on this result results qualitatively and quantitatively large.
We give an elementary discussion of parton saturation and its description by the effective theory of the Color Glass Condensate. We report on progress in calculating multi-gluon correlators. The latter are necessary for many phenomenological applications, upon some of which we briefly touch.
The Color Glass Condensate is a universal state of matter which can manifest itself in hadronic processes involving small-x partons, like DIS and pp, pA and AA collisions at high energy. Observables are given in terms of multi-gluon correlators, whose ensemble evolves according to a RG equation, the JIMWLK equation. We focus on recent progress towards its solution which lead to quasi-exact, analytic expressions for the multi-gluon correlators at high energy.
We modify the McLerran-Venugopalan model to include only a finite number of sources of color charge. We argue that Coulombic interactions between these color charges generates a source-source correlation function that properly includes the effects of color charge screening, a generalization of Debye screening for the Color Glass Condensate. Such a model may be useful for computing angular harmonics of flow measured in high energy hadron collisions for small systems. In this paper we provide a basic formulation of the problem on a lattice.
We extract the leading twist-2 and subleading twist-3 Distribution Amplitudes (DAs) of the rho meson using the HERA data on diffractive rho photoproduction. We do so using several Colour Glass Condensate (CGC) inspired and a Regge inspired dipole models. We find that our extracted twist-2 DA is not much model dependent and is consistent with QCD Sum Rules and lattice predictions. The extracted twist-3 DA is more model dependent but is still consistent with the Sum Rules prediction.
An exact analytical solution to the Balitsky-Kovchegov equation is proposed incorporating Mellin transformation with saddle point approximation. The theoretical significance of this solution is its simplicity in form which requires very less number of parameters. Using this solution along with the idea of color glass condensate, a very good description of RHIC and LHC data on differential yield is obtained for d-Au, p-p and p-Pb collisions. Quantitative prediction for the nuclear modification factors for p-Pb, Pb-Pb and Xe-Xe collisions relevant for very recent LHC run 2 is yielded.
We consider, for the first time, correlations between produced quarks in p-A collisions in the framework of the Color Glass Condensate. We find a quark-quark ridge that shows a dip at $Δη\sim 2$ relative to the gluon-gluon ridge. The origin of this dip is the short range (in rapidity) Pauli blocking experienced by quarks in the wave function of the incoming projectile. We observe that these correlations, present in the initial state, survive the scattering process. We suggest that this effect may be observable in open charm-open charm correlations at the Large Hadron Collider.
The similarities between string percolation and Glasma results are emphasized, special attention being paid to rapidity long range correlations, ridge structure and elliptic flow. As the string density of high multiplicity pp collisions at LHC energies has similar value as the corresponding to Au-Au semi-central collisions at RHIC we also expect in pp collisions long rapidity correlations and ridge structure, extended more than 8 units in rapidity.
We calculate the transverse correlation of fluctuations of the deposited energy density in nuclear collisions in the framework of the Gaussian color glass condensate model.
We discover new vacuum solutions of the JIMWLK equation, which correspond to center of a gauge group. We improve the color glass condensate (CGC) model by an explicit usage of a density matrix. Studying scattering of CGC states in an external color field, we observe that an amplitude is naturally expressed via group characters. We construct an example that shows how new thin effects may be potentially observed in peripheral collisions. We prove that at any parton density a gluonic CGC state does not become a true black disk. We find a wave function of a true black disk and show that it necessa…
We show that for a finite number of emitting sources, the Color Glass Condensate produces substantial elliptic azimuthal anisotropy, characterized by $v_2$, for two and four particle correlations for momentum greater than or of the order the saturation momentum. The flow produced has the correct semi-quantitative features to describe flow seen in LHC experiments with p-Pb and pp collisions. This flow is induced by quantum mechanical interference between the waves of produced particles, and the flow itself is coupled to fluctuations in the positions of emitting sources. We shortly discuss gener…
In this review, I present the description of the early stages of heavy ion collisions at high energy in the Color Glass Condensate framework, from the pre-collision high energy nuclear wavefunction to the point where hydrodynamics may start becoming applicable.
