A Brief Introduction to the Color Glass Condensate and the Glasma

On the gluon spectrum in the glasma

We study the gluon distribution in nucleus-nucleus collisions in the framework of the Color-Glass-Condensate. Approximate analytical solutions are compared to numerical solutions of the non-linear Yang-Mills equations. We find that the full numerical solution can be well approximated by taking the full initial condition of the fields in Coulomb gauge and using a linearized solution for the time evolution. We also compare kt-factorized approximations to the full solution.

Fluctuating Glasma initial conditions and flow in heavy ion collisions

We compute initial conditions in heavy-ion collisions within the Color Glass Condensate (CGC) framework by combining the impact parameter dependent saturation model (IP-Sat) with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this IP-Glasma description includes quantum fluctuations of color charges on the length-scale determined by the inverse nuclear saturation scale Q_s. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity is…

Rapidity long range correlations, parton percolation and color glass condensate

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.

Simulating collisions of thick nuclei in the color glass condensate framework

We present our work on the simulation of the early stages of heavy-ion collisions with finite longitudinal thickness in the laboratory frame in 3+1 dimensions. In particular we study the effects of nuclear thickness on the production of a glasma state in the McLerran-Venugopalan model within the color glass condensate framework. A finite thickness enables us to describe nuclei at lower energies, but forces us to abandon boost-invariance. As a consequence, random classical color sources within the nuclei have to be included in the simulation, which is achieved by using the colored particle-in-c…

Some Comments About The High Energy Limit of QCD

I argue that the physics of the scattering of very high energy strongly interacting particles is controlled by a new, universal form of matter, the Color Glass Condensate. This matter is the dominant contribution to the low x part of a hadron wavefunction. In collisions, this matter almost instantaneously turns into a Glasma. The Glasma initially has strong longitudinal color electric and magnetic fields, with topological charge. These fields melt into gluons. Due to instabilities, quantum noise is converted into classical turbulence, which may be responsible for the early thermalization seen …

Heavy Ion Collisions and New Forms of Matter

I discuss forms of high energy density matter in QCD. These include the Color Glass Condensate, the Glasma and the Quark Gluon Plasma. They all might be studied in ultra-relativistic heavy ion collisions, nd the Color Glass Condensate might also be probed in electron-hadron collisions. I present the properties of such matter and some aspects of what is known of their properties.

Glasma flux tubes and the near side ridge phenomenon at RHIC

We investigate the consequences of long range rapidity correlations in the Glasma. Particles produced locally in the transverse plane are correlated by approximately boost invariant flux tubes of longitudinal color electric and magnetic fields that are formed when two sheets of Colored Glass Condensate pass through one another, each acquiring a modified color charge density in the collision. We argue that such long range rapidity correlations persist during the evolution of the Quark Gluon Plasma formed later in the collision. When combined with transverse flow, these correlations reproduce ma…

3-D structure of the Glasma initial state -- Breaking boost-invariance by collisions of extended shock waves in classical Yang-Mills theory

We simulate the 3+1 D classical Yang-Mills dynamics of the collisions of longitudinally extended nuclei, described by eikonal color charges in the Color Glass Condensate framework. By varying the longitudinal thickness of the colliding nuclei, we discuss the violations of boost invariance and explore how the boost invariant high-energy limit is approached. Subsequently, we develop a more realistic model of the three dimensional color charge distributions that connects longitudinal and transverse fluctuations to the $x$ and $k_\bot$ dependence of transverse momentum dependent parton distributio…

Nonequilibrium axial charge production in expanding glasma flux tubes

Axial charge production at the early stage of heavy-ion collisions is investigated within the framework of real-time lattice simulations at leading order in QCD coupling. Starting from color glass condensate initial conditions, the time evolution of quantum quark fields under classical color gauge fields is computed on a lattice in longitudinally expanding geometry. We consider simple color charge distributions in Lorentz contracted nuclei that realize flux tube-like configurations of color fields carrying nonzero topological charge after a collision. By employing the Wilson fermion extended t…

Topological charge fluctuations in the Glasma

The early-time evolution of the system generated in ultra-relativistic heavy ion collisions is dominated by the presence of strong color fields known as Glasma fields. These can be described following the classical approach embodied in the Color Glass Condensate effective theory, which approximates QCD in the high gluon density regime. In this framework we perform an analytical first-principles calculation of the two-point correlator of the divergence of the Chern-Simons current at proper time $τ\!=\!0^+$, which characterizes the early fluctuations of axial charge density in the plane transver…

稀薄Glasma的若干方面

Aspects of the dilute Glasma

引入(3+1)D稀薄Glasma框架描述重离子碰撞的快度依赖性，通过线性化Yang-Mills方程推导场强张量，数值发现非Bjorken纵向流与极限碎裂特征，并探讨其在质子碰撞中的适用性。

基于色玻璃凝聚初始条件的强相互作用物质贝叶斯量化

Bayesian quantification of strongly-interacting matter with color glass condensate initial conditions

本研究结合IP-Glasma初始态等多阶段模型，对2.76 TeV铅+铅碰撞开展全局贝叶斯分析，获取强相互作用物质粘度等参数，首次在重离子分析中结合迁移学习推断与贝叶斯模型平均方法。

Gluon Saturation and the Formation Stage of Heavy Ion Collisions

The high energy limit of QCD is controlled by very high energy density gluonic matter, the Color Glass Condensate. In the first instants of the collisions of two sheets of Colored Glass Condensate, a Glasma is formed with longitudinal flux tubes of color electric and magnetic fields. These flux tubes decay and might form a turbulent liquid that eventually thermalizes into a Quark Gluon Plasma

相对论重离子碰撞的最早阶段

The earliest phase of relativistic heavy-ion collisions

本研究基于 Color Glass Condensate 框架，用固有时展开解析计算 glasma 的能量–动量张量及相关输运性质，并探讨其在喷注淬火中的作用。

Initial correlations of the Glasma energy-momentum tensor

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 ($\langle T^{μν}(x_{\perp})T^{σρ}(y_{\perp})\rangle$ and $\langle T^{μν}(x_{\perp})\rangle$, 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 t…

Wilson line correlator in the MV model: relating the glasma to deep inelastic scattering

In the color glass condensate framework the saturation scale measured in deep inelastic scattering of high energy hadrons and nuclei can be determined from the correlator of Wilson lines in the hadron wavefunction. These same Wilson lines give the initial condition of the classical field computation of the initial gluon multiplicity and energy density in a heavy ion collision. In this paper the Wilson line correlator in both adjoint and fundamental representations is computed using exactly the same numerical procedure that has been used to calculate gluon production in a heavy ion collision. I…

Initial Singularity of the Little Bang

The Color Glass Condensate (CGC) predicts the form of the nuclear wavefunction in QCD at very small x. Using this, we compute the wavefunction for the collision of two nuclei, infinitesimally in the forward light cone. We show that the Wigner transformation of this wavefunction generates rapidity dependent fluctuations around the boost invariant classical solution which describe the Glasma in the forward light cone.

The Status of Parton Saturation and the CGC

This is a personal summary of the meeting "Saturation, the Color Glass Condensate and Glasma: What Have we Learned from RHIC?" that took place at BNL in May 2010. The purpose of the meeting was to discuss the status of high density QCD and parton saturation, and to review the progress that RHIC has allowed in the field.

稀薄(3+1)D Glasma的能量-动量张量

Energy-momentum tensor of the dilute (3+1)D Glasma

本文在色玻璃凝聚框架下，利用广义McLerran-Venugopalan模型和蒙特卡罗积分，推导了(3+1)D Glasma能量-动量张量的简洁表达式，揭示了纵向流动偏离Bjorken流动的几何机制，并预测极限碎裂在LHC能量下成立。

Effect of non-eikonal corrections on azimuthal asymmetries in the Color Glass Condensate

We analyse the azimuthal structure of two gluon correlations in the Color Glass Condensate including those effects that result from relaxing the shockwave approximation for the target. Working in the Glasma graph approach suitable for collisions between dilute systems, we compute numerically the azimuthal distributions and show that both even and odd harmonics appear. We study their dependence on model parameters, energy of the collision, pseudorapidity and transverse momentum of the produced particles, and length of the target. While the contribution from non-eikonal corrections vanishes with…

Non-eikonal corrections to multi-particle production in the Color Glass Condensate

We consider the non-eikonal corrections to particle production in the Color Glass Condensate stemming from the relaxation of the shockwave approximation for the target that acquires a finite longitudinal dimension. We derive a modified expression of the Lipatov vertex which takes into account this finite target width. This expression is employed to compute single, double and triple gluon production in the Glasma graph limit valid for the scattering of two dilute objects, at all orders in the expansion in the number of colors. We justify and generalize previous results, and discuss the possible…

Color Glass Condensate in High Energy QCD

A brief review of major theoretical aspects of color glass condensate physics is given.

Color Glass Condensate in QCD at High Energy

I give a brief review about the color glass condensate, which is the universal form of hadrons and nuclei at high energies.

The Colour Glass Condensate

I briefly review the physical picture of the saturated gluons at small-x as a Colour Glass Condensate, and the effective theory which forms the basis of this picture.

Initial state effects in the Color Glass Condensate

The Color Glass Condensate provides a systematic power counting of initial state effects in high energy QCD. We briefly discuss in this framework quark and gluon production in high energy collisions.

The Color Glass Condensate and some applications

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.

High energy pA collisions in the Color Glass Condensate approach

We present a brief review of phenomenological applications of the gluon saturation approach to the proton-nucleus collisions at high energies.

The Color Glass Condensate: an overview

The Color Glass Condensate is a theory of the dynamical properties of partons in the Regge limit of QCD: x_{\rm Bj}\to 0$, $Q^2 >> Λ_{\rm QCD}^2={\rm fixed} and the center of mass energy squared s\to \infty. We provide a brief introduction to the theoretical ideas underlying the Color Glass Condensate and discuss the application of these ideas to high energy scattering in QCD.

Small x physics and RHIC data

This is a review of applications of the Color Glass Condensate to the phenomenology of relativistic heavy ion collisions. The initial stages of the collision can be understood in terms of the nonperturbatively strong nonlinear glasma color fields. We discuss how the CGC framework can and has been used to compute properties of the initial conditions of AA collisions. In particular this has led to recent progress in understanding multiparticle correlations, which can provide a directly observable signal of the properties of the initial stage of the collision process.

In the Shadow of the Color Glass

I give a brief overview of recent theoretical progress within perturbative QCD concerning the high-energy dynamics in the vicinity of the unitarity limit. Special attention is payed to the most recent developments concerning the relation between high-energy QCD and statistical physics, the role of the pomeron loops, and the transition from geometric scaling to diffusive scaling with increasing energy.

Color Glass Condensate and its relation to HERA physics

I give a brief overview of the effective theory for the Color Glass Condensate, which is the high-density gluonic matter which controls high-energy scattering in QCD in the vicinity of the unitarity limit. I concentrate on fundamental phenomena, like gluon saturation, unitarization, and geometric scaling, and the way how these are encoded in the formalism. I emphasize the importance of the next-to-leading order corrections, especially the running of the coupling, for both conceptual and phenomenological issues. I survey the implications of the CGC theory for the HERA physics and its phenomenol…

Hybrid Color Glass Condensate and hydrodynamic description of the Relativistic Heavy Ion Collider small system scan

Multi-particle correlation observables in the Relativistic Heavy Ion Collider small system scan are computed in a framework that contains both initial state momentum anisotropies from the Color Glass Condensate effective theory and final state hydrodynamic evolution. The initial state is computed using the IP-Glasma model and coupled to viscous relativistic hydrodynamic simulations, which are followed by microscopic hadronic transport. All parameters of the calculation were previously constrained using experimental data on Au+Au collisions at the same center of mass energy. We find that the qu…

Energy Dependent Growth of Nucleon and Inclusive Charged Hadron Distributions

In the Color Glass Condensate formalism, charged hadron p_{T} distributions in p+p collisions are studied by considering an energy-dependent broadening of nucleon's density distribution. Then, in the Glasma flux tube picture, the n-particle multiplicity distributions at different pseudo-rapidity ranges are investigated. Both of the theoretical results show good agreement with the recent experimental data from ALICE and CMS at \sqrt{s}=0.9, 2.36, 7 TeV. The predictive results for p_{T} and multiplicity distributions in p+p and p+Pb collisions at the Large Hadron Collider are also given in this …

Nonlinear evolution equations in QCD and effective Hamiltonian at high energy

In this talk I briefly present recent developments in the theory of the Color Glass Condensate. The duality between the dense and dilute regimes of the gluon field is discussed as well as the effective selfdual Hamiltonian which includes both Pomeron merging and Pomeron splitting.

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.

QCD Color Glass Condensate Model in Warped Brane Models

Hadron-hadron interaction and Deep Inelastic Scattering (DIS) at very high energies is dominated by events at small-$x_B$ regime. Interesting and complex physical content of this regime is described by a phenomenological model called McLerran-Venugopalan Color Glass Condensate (MVCGC) model. The advantage of this formalism is the existence of a renormalization-type equation which relates directly observable low energy (small-$x_B$) physics to high energy scales where one expects the appearance of phenomena beyond Standard model. After a brief argument about complexity of observations and their…

Introduction to the Physics of Saturation

We present a brief introduction to the physics of parton saturation/Color Glass Condensate (CGC).

The initial state of heavy-ion collisions

We present a brief review of recent theoretical developments and related phenomenological approaches for understanding the initial state of heavy-ion collisions, with emphasis on the Color Glass Condensate formalism.