Color-glass condensate

About: Color-glass condensate is a research topic. Over the lifetime, 885 publications have been published within this topic receiving 35169 citations.

Initial correlations of the Glasma energy-momentum tensor

Abstract: We present an analytical calculation of the covariance of the energy-momentum tensor associated to the gluon field produced in ultra-relativistic heavy ion collisions at early times, the Glasma. This object involves the two-point and single-point correlators of the energy-momentum tensor (〈Tμν (x⊥)Tσρ(y⊥)〉 and 〈Tμν (x⊥)〉, respectively) at proper time τ = 0+. Our approach is based on the Color Glass Condensate effective theory, which allows us to map the fluctuations of the valence color sources in the colliding nuclei to those of the energy-momentum tensor of the produced gluon fields via the solution of the classical equations of motion in the presence of external currents. The color sources in the two colliding nuclei are characterized by Gaussian correlations, albeit in more generality than in the McLerran-Venugopalan model, allowing for non-trivial impact parameter and transverse dependence of the two-point correlator. We compare our results to those obtained under the Glasma Graph approximation, finding agreement in the limit of short transverse separations. However, important differences arise at larger transverse separations, where our result displays a slower fall-off than the Glasma Graph result (1/r2 vs. 1/r4 power-law decay), indicating that the color screening of the correlations in the transverse plane occurs at distances larger than 1/Qs by a logarithmic factor sensitive to the infrared. In the Glasma flux tube picture, this implies that the color domains are larger than originally estimated.

Near-Fields and Initial Energy Density in High Energy Nuclear Collisions

Abstract: We calculate the classical gluon field created at early times in collisions of large nuclei at high energies. We find that the field is dominated by the longitudinal chromoelectric and chromomagnetic components. We estimate the initial energy density of this gluon field to be approximately 260 GeV/fm 3 at RHIC. sions of gold nuclei at √ sNN = 200 GeV energy densities far in excess of the critical value required for deconfine- ment (ǫc ≈ 2 GeV/fm 3 ) are reached (1). Furthermore, the partonic phase seems to be thermalized after a very short time τ0 < 1 fm/c. While the evolution of the quark gluon plasma in equilibrium can be described by rela- tivistic hydrodynamics (2), the initial soft interactions of the nuclei and the thermalization process before the time τ0 are still not completely understood. It has been argued that the initial dynamics for the collision of two very high energy nuclei is determined by a universal phase called the color glass condensate (CGC). This idea is based on gluon saturation at a scale Qs (3, 4, 5, 6, 7). Slowly evolving and randomly distributed color charges in the nuclei are the sources of this gluon field. A simple implementation is the McLerran-Venugopalan (MV) model (3, 4) in which the gluon field is given by the solution of the classical Yang-Mills equations. In this Letter we calculate the gluon field at early times after the collision in the framework of the McLerran- Venugopalan model. We use an expansion of the Yang- Mills equations in powers of the proper time τ. This is a near-field approximation which may be the most appro- priate use of the color glass condensate picture. We also estimate the initial energy density at the time of overlap of the nuclei using a simple model for the nuclear gluon distribution and coarse-graining methods to avoid ultra- violet (UV) singularities. More details and a discussion of applications will be provided elsewhere (8). In high energy collisions the two colliding nuclei are highly Lorentz contracted; therefore, the valence and large-x partons are described by infinitesimally thin sheets propagating on the light cone. Although each nu- cleus is color neutral as a whole, local color fluctuations do occur. At the moment of overlap, the color distribu- tions in nucleus 1 (+ light cone) and 2 (− light cone) are ρ1(x⊥) and ρ2(x⊥), respectively. We use light cone

Quark production in heavy ion collisions: formalism and boost invariant fermionic light-cone mode functions

Abstract: We revisit the problem of quark production in high energy heavy ion collisions, at leading order in α s in the color glass condensate framework. In this first paper, we setup the formalism and express the quark spectrum in terms of a basis of solutions of the Dirac equation (the mode functions). We determine analytically their initial value in the Fock-Schwinger gauge on a proper time surface Q s τ 0 ≪ 1, in a basis that makes manifest the boost invariance properties of this problem. We also describe a statistical algorithm to perform the sampling of the mode functions.

A Short Course on Relativistic Heavy-Ion Collisions

Abstract: Relativistic heavy ion collision is a fascinating field of research. In recent years, the field has seen an unprecedented level of progress. A new state of matter, deconfined quark–gluon plasma (QGP), was predicted. An accelerator was built to detect this new state of matter. Experiments were performed and the discovery of the 'most perfect fluid' was made. Conclusive identification of the most perfect fluid state with the deconfined state has yet to be achieved. One of the impediments towards such identification is the fundamental property of the strong interaction, the 'color confinement', i.e. the constituents of the theory, the 'colored' quarks and gluons, are confined within a hadron. Any information about the deconfined state must be amassed from the color-neutral hadrons. And yet the process by which colored building blocks convert into a color singlet state is not properly understood. This necessitates model building. To young researchers, the field poses a problem in that it is multi-disciplinary, requiring knowledge of thermodynamics, statistical physics, kinetic theory, group theory, quantum chromodynamics (QCD), etc. The complexity of heavy ion collisions has necessarily led to a proliferation of models, e.g. the thermal model, blast wave model hydrodynamic model and models based on transport equations, etc, the physics of which need to be understood.