Showing papers on "Color-glass condensate published in 2010"

The Color Glass Condensate

Abstract: We provide a broad overview of the theoretical status and phenomenological applications of the Color Glass Condensate effective field theory describing universal properties of saturated gluons in hadron wavefunctions that are extracted from deeply inelastic scattering and hadron-hadron collision experiments at high energies.

The Colour Glass Condensate

Abstract: 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.

Event-by-Event Simulation of the Three-Dimensional Hydrodynamic Evolution from Flux Tube Initial Conditions in Ultrarelativistic Heavy Ion Collisions

Abstract: We present a sophisticated treatment of the hydrodynamic evolution of ultrarelativistic heavy ion collisions, based on the following features: initial conditions obtained from a flux tube approach, compatible with the string model and the color glass condensate picture; an event-by-event procedure, taking into the account the highly irregular space structure of single events, being experimentally visible via so-called ridge structures in two-particle correlations; the use of an efficient code for solving the hydrodynamic equations in $3+1$ dimensions, including the conservation of baryon number, strangeness, and electric charge; the employment of a realistic equation of state, compatible with lattice gauge results; the use of a complete hadron resonance table, making our calculations compatible with the results from statistical models; and a hadronic cascade procedure after hadronization from the thermal matter at an early time.

Azimuthal correlations of forward dihadrons in d + Au collisions at RHIC in the color glass condensate.

Abstract: We present a good description of recent experimental data on forward dihadron azimuthal correlations measured in deuteron-gold collisions at the BNL Relativistic Heavy Ion Collider (RHIC), where monojet production has been observed. Our approach is based on the color glass condensate theory for the small-x degrees of freedom of the nuclear wave function, including the use of nonlinear evolution equations with running QCD coupling. Our analysis provides further evidence for the presence of saturation effects in RHIC data.

Dissipative transport of a Bose-Einstein condensate

Abstract: We investigate the effects of impurities, either correlated disorder or a single Gaussian defect, on the collective dipole motion of a Bose-Einstein condensate of {sup 7}Li in an optical trap. We find that this motion is damped at a rate dependent on the impurity strength, condensate center-of-mass velocity, and interatomic interactions. Damping in the Thomas-Fermi regime depends universally on the disordered potential strength scaled to the condensate chemical potential and the condensate velocity scaled to the speed of sound. The damping rate is comparatively small in the weakly interacting regime, and, in this case, is accompanied by strong condensate fragmentation. In situ and time-of-flight images of the atomic cloud provide evidence that this fragmentation is driven by dark soliton formation.

Hadron multiplicity in pp and AA collisions at LHC from the color glass condensate

Abstract: We provide quantitative predictions for the rapidity, centrality and energy dependencies of inclusive charged-hadron productions for the forthcoming LHC measurements in nucleus-nucleus collisions based on the idea of gluon saturation in the color-glass condensate framework. Our formulation gives very good descriptions of the first data from the LHC for the inclusive charged-hadron production in proton-proton collisions, the deep inelastic scattering at the Hadron-Elektron-Ring-Anlage at small Bjorken x, and the hadron multiplicities in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider.

Saturation and Scaling of Multiplicity, Mean $p_T$ and $p_T$ Distributions from 200 GeV < sqrt{s) < 7 TeV

Abstract: The multiplicity, average transverse momentum, and charged particle transverse momentum distributions have recently been measured in LHC experiments. The multiplicity and average transverse momentum grow with beam energy. Such growth is expected in the theory of the Color Glass Condensate, a theory that incorporates the physics of saturation into the evolution of the gluon distribution. We show that the energy dependence of the $p\overline{p}$ data and the LHC data for $pp$ scattering at \sqrt{s} > 200 GeV may be simply described using a minimal amount of model input. Such a description uses parameters consistent with the Color Glass Condensate descriptions of HERA and RHIC experimental data.

Small x physics and RHIC data

Abstract: 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.

v 4 from ideal and viscous hydrodynamic simulations of nuclear collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC)

Abstract: We compute v{sub 4}/(v{sub 2}){sup 2} in ideal and viscous hydrodynamics. We investigate its sensitivity to details of the hydrodynamic model and compare the results to experimental data from the BNL Relativistic Heavy Ion Collider (RHIC). Whereas v{sub 2} has a significant sensitivity only to initial eccentricity and viscosity while being insensitive to freeze-out temperature, we find that v{sub 4}/(v{sub 2}){sup 2} is quite insensitive to initial eccentricity. On the other hand, it can still be sensitive to shear viscosity in addition to freeze-out temperature, although viscous effects do not universally increase v{sub 4}/(v{sub 2}){sup 2} as originally predicted. Consistent with data, we find no dependence on particle species. We also make a prediction for v{sub 4}/(v{sub 2}){sup 2} in heavy ion collisions at the CERN Large Hadron Collider (LHC).

Suppression of Forward Pion Correlations in d+Au Interactions at STAR

Abstract: During the 2008 run RHIC provided high luminosity in both p+p and d+Au collisions at $\sqrt{s_{NN}}=200GeV$. Electromagnetic calorimeter acceptance in STAR was enhanced by the new Forward Meson Spectrometer (FMS), and is now almost contiguous from $-1<\eta<4$ over the full azimuth. This large acceptance provides sensitivity to the gluon density in the nucleus down to $x\approx 10^{-3}$. Measurements of the azimuthal correlation between a forward $\pi^0$ and an associated particle at large rapidity are sensitive to the low-$x$ gluon density. Data exhibit the qualitative features expected from gluon saturation. A comparison to calculations using the Color Glass Condensate (CGC) model is presented.

The quark–gluon medium

Abstract: The properties of the quark–gluon medium observed in high-energy nucleus–nucleus collisions are discussed. The main experimental facts about these collisions are briefly described and compared with data about proton–proton collisions. Both microscopic and macroscopic approaches to their description are reviewed. The chromodynamics of the quark–gluon medium at high energies is mainly considered. The energy loss of partons moving in this medium is treated. The principal conclusion is that the medium possesses some collective properties which are crucial for understanding the experimental observations.

Kaon and pion femtoscopy at the highest energies available at the BNL Relativistic Heavy Ion Collider (RHIC) in a hydrokinetic model

Abstract: The hydrokinetic approach that incorporates hydrodynamic expansion of the systems formed in A+A collisions and their dynamical decoupling is applied to restore the initial conditions and space-time picture of the matter evolution in central Au+Au collisions at the top Relativistic Heavy Ion Collider energy. The analysis is based on the detailed reproduction of the pion and kaon momentum spectra and femtoscopic data in whole interval of the transverse momenta studied by both the STAR and the PHENIX collaborations. The fitting procedure utilizes the two parameters: the maximal energy density at supposed thermalization time 1 fm/c and the strength of the prethermal flows developed to this time. The quark-gluon plasma and hadronic gas is supposed to be in complete local equilibrium above the chemical freeze-out temperature T{sub ch}=165 MeV with the equation of states (EoS) at high temperatures as in the lattice QCD. Below T{sub ch} the EoS in the expanding and gradually decoupling fluid depends on the composition of the hadron-resonance gas at each space-time point and accounts for decays of resonances into the nonequilibrated medium. A good description of the pion and kaon transverse momentum spectra and interferometry radii is reached at both used initial energy density profiles motivatedmore » by the Glauber and color glass condensate models, however, at different initial energy densities. The discussion as for the approximate pion and kaon m{sub T} scaling for the interferometry radii is based on a comparison of the emission functions for these particles.« less

Hadrons and direct photon production in pp and pA collisions at the LHC and saturation effects

Abstract: We investigate hadrons and direct photon production in pp and pA collisions at the energies of RHIC and LHC within the color-dipole approach employing various saturation models. We show that greatest sensitivity to saturation effects is reached at very forward rapidities for pp collisions at LHC ({radical}(s)=14 TeV). The ratio of direct-photon to pion {gamma}/{pi}{sup 0} production can be about 20 divide 10 (at {eta}=7 divide 8). Therefore, direct photon production at forward rapidities should provide a rather clean probe. We calculate the rapidity dependence of the invariant cross section and find some peculiar enhancement at forward rapidities which is more pronounced for direct photon production. We show that this peak is further enhanced by saturation effects. We provide predictions for the nuclear modification factor R{sub pA} for pions and direct photon production in pA collisions at LHC energy at midrapidity. We show within various saturation models that the pion Cronin enhancement at RHIC is replaced by a moderate suppression at LHC energy at midrapidity due to gluon shadowing effects. Cronin enhancement of direct photons can survive at LHC energy within models with a larger saturation scale.

Saturation and Scaling of Multiplicity, Mean p_T and p_T Distributions from 200 GeV < sqrt{s} < 7 TeV

Abstract: The multiplicity, average transverse momentum, and charged particle transverse momentum distributions have recently been measured in LHC experiments. The multiplicity and average transverse momentum grow with beam energy. Such growth is expected in the theory of the Color Glass Condensate, a theory that incorporates the physics of saturation into the evolution of the gluon distribution. We show that the energy dependence of the $p\overline{p}$ data and the LHC data for $pp$ scattering at \sqrt{s} > 200 GeV may be simply described using a minimal amount of model input. Such a description uses parameters consistent with the Color Glass Condensate descriptions of HERA and RHIC experimental data.

Testing non-linear evolution with running coupling corrections in ep and pp collisions

Abstract: Perturbative QCD predicts that the growth of the gluon density at small x (high energies) should saturate, forming a Color Glass Condensate (CGC), which is described in mean field approximation by the Balitsky–Kovchegov (BK) equation. Recently, the next-to-leading order corrections for the BK equation were derived and a global fit of the inclusive ep HERA data was performed, resulting in a parameterization for the forward scattering amplitude. In this paper we compare this parameterization with the predictions of other phenomenological models and investigate the saturation physics in diffractive deep-inelastic electron–proton scattering and in the forward hadron production in pp collisions. Our results demonstrate that the running coupling BK solution is able to describe these observables.

Strongly Interacting Matter Matter at Very High Energy Density: 3 Lectures in Zakopane

Abstract: These lectures concern the properties of strongly interacting matter at very high energy density. I begin with the Color Glass Condensate and the Glasma, matter that controls the earliest times in hadronic collisions. I then describe the Quark Gluon Plasma, matter produced from the thermalized remnants of the Glasma. Finally, I describe high density baryonic matter, in particular Quarkyonic matter. The discussion will be intuitive and based on simple structural aspects of QCD. There will be some discussion of experimental tests of these ideas.

Strongly Interacting Matter Matter at Very High Energy Density: 3 Lectures in Zakopane

Abstract: These lectures concern the properties of strongly interacting matter at very high energy density. I begin with the Color Glass Condensate and the Glasma, matter that controls the earliest times in hadronic collisions. I then describe the Quark Gluon Plasma, matter produced from the thermalized remnants of the Glasma. Finally, I describe high density baryonic matter, in particular Quarkyonic matter. The discussion will be intuitive and based on simple structural aspects of QCD. There will be some discussion of experimental tests of these ideas.

Gluon saturation and inclusive production at low transverse momenta

Abstract: In this paper we suggest the generalization of k T factorization formula for inclusive gluon production for the dense-dense parton system scattering. It turns out that the soft gluon production with transverse momentum p T is suppressed by an additional Sudakov-like factor that depends on the p 2 T /Q 2 s ratio in good agreement with the first numerical calculation in the color glass condensate approach by J. P. Blaizot, T. Lappi, and Y. Mehtar-Tan.

Strongly Interacting Matter at High Energy Density

Abstract: This lecture concerns the properties of strongly interacting matter (which is described by Quantum Chromodynamics) at very high energy density. I review the properties of matter at high temperature, discussing the deconfinement phase transition. At high baryon density and low temperature, large N{sub c} arguments are developed which suggest that high baryonic density matter is a third form of matter, Quarkyonic Matter, that is distinct from confined hadronic matter and deconfined matter. I finally discuss the Color Glass Condensate which controls the high energy limit of QCD, and forms the low x part of a hadron wavefunction. The Glasma is introduced as matter formed by the Color Glass Condensate which eventually thermalizes into a Quark Gluon Plasma.

Hadron Multiplicities in Pb+Pb Collisions at the Large Hadron Collider and Pomeron Loop Effects

Abstract: We study the pseudo-rapidity distribution of hadron multiplicities of high energy Pb+Pb collisions by using color glass condensate dynamics at LHC/ALICE in the fixed coupling case. It is found that after including the pomeron loop effects the charged hadron multiplicities at central rapidity are about 1500 for central Pb+Pb collisions, which are significantly smaller than the saturation based calculations, ~ 1700 ÷ 2500 and compatible with that based on a study of multiplicities in the fragmentation region.

Suppression of Forward Pion Correlations in d+Au Interactions at STAR

Abstract: During the 2008 run RHIC provided high luminosity in both p+p and d+Au collisions at $\sqrt{s_{NN}}=200GeV$. Electromagnetic calorimeter acceptance in STAR was enhanced by the new Forward Meson Spectrometer (FMS), and is now almost contiguous from $-1<\eta<4$ over the full azimuth. This large acceptance provides sensitivity to the gluon density in the nucleus down to $x\approx 10^{-3}$. Measurements of the azimuthal correlation between a forward $\pi^0$ and an associated particle at large rapidity are sensitive to the low-$x$ gluon density. Data exhibit the qualitative features expected from gluon saturation. A comparison to calculations using the Color Glass Condensate (CGC) model is presented.

Rapidity long range correlations, parton percolation and color glass condensate

Abstract: 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.

The CGC and the Glasma: Two Lectures at the Yukawa Institute

Abstract: These lectures present the theory of the Color Glass Condensate (CGC) and the Glasma in an elementary and intuitive manner. This matter controls the high energy limit of QCD. The CGC is the universal limit for the components of a hadron wavefunction important for high energy scattering processes. It is a highly coherent, extremely high energy density ensemble of gluon states. The Glasma is matter produced in the collision of CGCs of two hadrons. It has properties much different from those of the CGC, and is produced in a very short time after the collision. It eventually evolves from the the Color Glass Condensate initial conditions into a Quark Gluon Plasma. We can visualize the collision of two high energy hadrons as shown in Fig. 1. Before the collision, two hadrons appear as Lorentz contracted sheets approaching one another at near light speed. These we will later describe as two sheets of Colored Glass. In a very short time, the sheets of Color Glass interpenetrate one another. This we think of as the initial singularity for the collision. This is of course not a real singularity for finite collision energy, but we will see it becomes one in the limit of infinite energy. After the initial singularity, a Glasma is formed. This is composed of highly coherent gluon fields of very high energy density. If we imagine that the sheets of Colored Glass have passed through one another largely intact, the Glasma forms in the region between the receding sheets. As time goes on, the Glasma evolves into a Quark Gluon Plasma, and eventually into a gas of ordinary hadrons. These lectures are about the earliest stages of these collisions, and will describe neither the Quark Gluon Plasma nor the Hadron Gas. I will motivate the CGC and Glasma from simple physical considerations, and provide a sketchy derivation from QCD. There will be some discussion of experimental tests of these ideas.