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Showing papers on "Color-glass condensate published in 2007"


Journal ArticleDOI
TL;DR: In this article, the authors derived forward inclusive dijet production in the scattering of a dilute hadron off an arbitrary dense target, whose partons with small fraction of momentum x are described by a color glass condensate.

197 citations


Proceedings ArticleDOI
21 Mar 2007
TL;DR: In this paper, a brief overview of recent theoretical developments within perturbative QCD concerning the high energy dynamics in the vicinity of the unitarity limit is given, along with a detailed discussion of the related theoretical developments.
Abstract: I give a brief overview of recent theoretical developments within perturbative QCD concerning the high‐energy dynamics in the vicinity of the unitarity limit.

188 citations


Journal ArticleDOI
TL;DR: In this paper, a modified form of the Kharzeev-Levin-Nardi (KLN) approach for nuclear collisions is introduced, which preserves factorization, and the saturation scale is bound from below by that for a single nucleon.
Abstract: We introduce a modified form of the Kharzeev-Levin-Nardi (KLN) approach for nuclear collisions. The new ansatz for the unintegrated gluon distribution function preserves factorization, and the saturation scale is bound from below by that for a single nucleon. It also reproduces the correct scaling with the number of collisions at high transverse momentum. The corresponding Monte Carlo implementation allows us to account for fluctuations of the hard sources (nucleons) in the transverse plane. We compute various definitions of the eccentricity within the new approach, which are relevant for the interpretation of the elliptic flow. Our approach predicts breaking of the scaling of the eccentricity with the Glauber eccentricity at the level of about 30%.

153 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that the centrality and system-size dependence of elliptic flow measured at the BNL Relativistic Heavy Ion Collider (RHIC) are fully described by a simple model based on eccentricity scaling and incomplete thermalization.
Abstract: We show that the centrality and system-size dependence of elliptic flow measured at the BNL Relativistic Heavy Ion Collider (RHIC) are fully described by a simple model based on eccentricity scaling and incomplete thermalization. We argue that the elliptic flow is at least 25% below the (ideal) ``hydrodynamic limit,'' even for the most central Au-Au collisions. This lack of perfect equilibration allows for estimates of the effective parton cross section in the quark-gluon plasma and of its viscosity to entropy density ratio. We also show how the initial conditions affect the transport coefficients and thermodynamic quantities extracted from the data, in particular, the viscosity and the speed of sound.

151 citations


Journal ArticleDOI
TL;DR: In this article, the initial eccentricity of heavy-ion collisions was determined via a Monte Carlo implementation of a color glass condensate factorization approach, and the eccentricity fluctuations were found to nearly saturate elliptic flow fluctuations measured recently at RHIC.
Abstract: In this Rapid Communication, we determine the fluctuations of the initial eccentricity in heavy-ion collisions caused by fluctuations of the nucleon configurations. This is done via a Monte Carlo implementation of a color glass condensate ${k}_{t}$-factorization approach. The eccentricity fluctuations are found to nearly saturate elliptic flow fluctuations measured recently at RHIC. Extrapolations to LHC energies are shown.

96 citations


Journal ArticleDOI
TL;DR: In this article, the initial eccentricity in heavy-ion collisions caused by fluctuations of the nucleon configurations was determined via a Monte-Carlo implementation of a Color Glass Condensate $k_t$-factorization approach.
Abstract: In this brief note, we determine the fluctuations of the initial eccentricity in heavy-ion collisions caused by fluctuations of the nucleon configurations. This is done via a Monte-Carlo implementation of a Color Glass Condensate $k_t$-factorization approach. The eccentricity fluctuations are found to nearly saturate elliptic flow fluctuations measured recently at RHIC. Extrapolations to LHC energies are shown.

93 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the produced gluon spectrum becomes thermal (in three dimensions) with an effective temperature determined by the saturation momentum Q{sub s,T=cQ{subs}/2{pi} during the time {approx} 1/T; they estimate c={radical}(2{π})/2{approx_equal}1.2.
Abstract: We argue that multiparticle production in high energy hadron and nuclear collisions can be considered as proceeding through the production of gluons in the background classical field. In this approach we derive the gluon spectrum immediately after the collision and find that at high energies it is parametrically enhanced by ln(1/x) with respect to the quasiclassical result (x is the Bjorken variable). We show that the produced gluon spectrum becomes thermal (in three dimensions) with an effective temperature determined by the saturation momentum Q{sub s},T=cQ{sub s}/2{pi} during the time {approx}1/T; we estimate c={radical}(2{pi})/2{approx_equal}1.2. Although this result by itself does not imply that the gluon spectrum will remain thermal at later times, it has an interesting applications to heavy ion collisions. In particular, we discuss the possibility of Bose-Einstein condensation of the produced gluon pairs and estimate the viscosity of the produced gluon system.

92 citations


Journal ArticleDOI
TL;DR: In this paper, the wave function for the collision of two nuclei, infinitesimally in the forward light cone, is computed and the Wigner transformation of this wave function generates rapidity dependent fluctuations around the boost invariant classical solution.

87 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss forward-backward correlations in the multiplicity of produced particles in heavy ion collisions and find that the color glass condensate generates distinctive predictions for the long range component of this correlation.

83 citations


Journal ArticleDOI
TL;DR: In this paper, a series of three lectures on high energy scattering among hadrons in Quantum Chromodynamics is presented. Butler et al. describe the parton model, Bjorken scaling and the scaling violations due to the evolution of parton distributions with the transverse resolution scale.
Abstract: In this series of three lectures, we discuss several aspects of high energy scattering among hadrons in Quantum Chromodynamics. The first lecture is devoted to a description of the parton model, Bjorken scaling and the scaling violations due to the evolution of parton distributions with the transverse resolution scale. The second lecture describes parton evolution at small momentum fraction x, the phenomenon of gluon saturation and the Color Glass Condensate (CGC). In the third lecture, we present the application of the CGC to the study of high energy hadronic collisions, with emphasis on nucleus-nucleus collisions. In particular, we provide the outline of a proof of high energy factorization for inclusive gluon production.

78 citations


Journal ArticleDOI
TL;DR: In this article, a brief review of phenomenological applications of the gluon saturation approach to the proton-nucleus collisions at high energies is presented, along with a detailed discussion of the effects of the saturation approach.

Journal ArticleDOI
TL;DR: The odderon is now a fundamental object in QCD and it has to be found experimentally if QCD is right as mentioned in this paper, and the most spectacular signature of the odderone is the predicted difference between the differential cross-sections for proton-proton and antiprotonproton at high s and moderate t.
Abstract: The odderon remains an elusive object, 33 years after its invention. The odderon is now a fundamental object in QCD and it has to be found experimentally if QCD is right. In the present paper, we show how to find it at RHIC and LHC. The most spectacular signature of the odderon is the predicted difference between the differential cross-sections for proton–proton and antiproton–proton at high s and moderate t. This experiment can be done by using the STAR detector at RHIC and by combining these future data with the already present UA4/2 data. The odderon could also be found by the ATLAS experiment at LHC by performing a high-precision measurement of the real part of the hadron elastic scattering amplitude at small t.

Journal ArticleDOI
TL;DR: In this paper, the initial energy density of the color glass condensate (CGC) was calculated in the early stage of the relativistic nucleus-nucleus collision at the BNL Relativistic Heavy Ion Collider.
Abstract: Color Glass Condensate (CGC) provides a classical description of dense gluon matter at high energies. Using the McLerran-Venugopalan (MV) model we calculate the initial energy density {epsilon}({tau}) in the early stage of the relativistic nucleus-nucleus collision. Our analytical formula reproduces the quantitative results from lattice discretized simulations and leads to an estimate {epsilon}({tau}=0.1 fm)=40{approx}50 GeV{center_dot}fm{sup -3} in the (central) Au-Au collision at BNL Relativistic Heavy Ion Collider. We then formulate instabilities with respect to soft fluctuations that violate boost invariance inherent in hard CGC backgrounds. We find unstable modes arising, which are attributed to ensemble average over the initial CGC fields.

Journal ArticleDOI
TL;DR: In this article, the Gaussian average of Wilson lines inherent in the Color Glass Condensate was computed for the scattering amplitude in the collision of a light projectile and a heavy target.
Abstract: We systematically compute the Gaussian average of Wilson lines inherent in the Color Glass Condensate, which provides useful formulae for evaluation of the scattering amplitude in the collision of a light projectile and a heavy target.

Journal ArticleDOI
TL;DR: In this article, the heavy quark production in the interaction of ultra high energy cosmic rays in the atmosphere, considering that the primary cosmic ray is a proton or a photon, is estimated.
Abstract: In this work we estimate the heavy quark production in the interaction of ultra high energy cosmic rays in the atmosphere, considering that the primary cosmic ray is a proton or a photon. At these energies the saturation momentum Qsat2(x) stays above the hard scale ?c2 = 4mc2, implying charm production probing the saturation regime. In particular, we show that the ep HERA data presents a scaling on ?c ? (Q2?+??c2)/Qsat2(x). We derive our results considering the dipole picture and the Color Glass Condensate formalism, which one shows to be able to describe the heavy quark production in ?p and pp collisions. Nuclear effects are considered for the scattering of primaries with the air nuclei and we provide a parametrization for the charm and bottom differential cross sections, d?/dxF, which can be used as an input for numerical implementations for lepton flux. Implications on the flux of prompt leptons at the Earth are analyzed and a large suppression is predicted.

Journal ArticleDOI
TL;DR: In this article, the long-range correlations between multiplicities in different rapidity windows in hadron-nucleus collisions are analyzed in the framework of perturbative QCD.
Abstract: Long-range correlations between multiplicities in different rapidity windows in hadron-nucleus collisions are analyzed. After recalling the standard results in the probabilistic model, we study them in the framework of perturbative QCD. Considering interacting BFKL pomerons in the form of fan diagrams coupled to a dilute projectile, analytic estimates are done for very large rapidities. The correlation strength results weakly depending on energy and centrality or nuclear size and generically greater than unity. Finally, we turn to the color glass condensate framework. For a saturated projectile and considering the most feasible experimental situation of forward and backward rapidity windows symmetric around the center-of-mass, the resulting correlation strength turns out to be larger than unity and shows a nonmonotonic behavior with increasing energy, first increasing and then decreasing to a limiting value. Its behavior with increasing centrality or nuclear size depends on the considered rapidity windows.

Journal ArticleDOI
TL;DR: In this paper, the Drell-Yan production cross section and structure functions in proton (deuteron)-nucleus collisions using the color glass condensate formalism were studied.
Abstract: We study the Drell-Yan production cross section and structure functions in proton (deuteron)-nucleus collisions using the color glass condensate formalism. The nucleus is treated in the color glass condensate framework which includes both higher twist effects due to the inclusion of multiple scatterings and leading twist pQCD shadowing due to the small x resummation, while the proton (or deuteron) is treated within the DGLAP improved parton model. In particular, the Drell-Yan structure functions are used in order to investigate the Lam-Tung relation at small x, which is known to be identically zero at leading twist up to next-to-leading order, and is thus a good playground for studying higher twist effects. In agreement with this, we find that violations of this relation are more important for low momentum and invariant mass of the Drell-Yan pair, and also in the region of rapidity that corresponds to smaller values of x in the nucleus.

Journal ArticleDOI
TL;DR: In this article, two particle azimuthal correlations between trigger particles at mid-rapidity and associated particles at forward rapidities (2.7 and 3.9) in p+p, d+Au, and Au + Au collisions at 200 GeV were presented.
Abstract: In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}} $= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.

Journal ArticleDOI
TL;DR: In this article, the authors 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.

Journal ArticleDOI
TL;DR: In this paper, the authors calculated the nuclear modification factor for the stopped baryons in the quasi-classical approximation and suppression at high energies/rapidities when quantum evolution corrections are included, providing a new observable which can be used to test Color Glass physics.

14 May 2007
TL;DR: In this article, the predicted multiplicities in pp, pA and AA collisions at the LHC were predicted based on the Color Glass Condensate (CGC) approach.
Abstract: We present the predictions for hadron multiplicities in pp, pA and AA collisions at the LHC based on our approach to the Color Glass Condensate.

Proceedings ArticleDOI
19 Jun 2007
TL;DR: 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 as mentioned in this paper, which is the dominant contribution to the low x part of a hadron wavefunction.
Abstract: 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 mater 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 in heavy ion collisions at RHIC.

Journal ArticleDOI
TL;DR: In this article, some general properties of particle production in a field theory coupled to strong time dependent sources are discussed, and techniques to compute the spectrum of the produced particles in such theories are presented.

Journal ArticleDOI
Tuomas Lappi1
TL;DR: In this paper, 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.
Abstract: 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. In particular the discretization of the longitudinal coordinate has a large numerical effect on the relation between the color charge density parameter g^2 mu and the saturation scale Qs. Our result for this relation is Qs = 0.6 g^2 mu, which results in the classical Yang-Mills value for the "gluon liberation coefficient" c = 1.1.

Journal ArticleDOI
TL;DR: In this paper, the results obtained in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory are discussed along with observables studied at energies lower than those at RHIC (particle production ratios, soft spectra, flows, and so on).
Abstract: Some results obtained in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory are discussed. Along with observables studied at energies lower than those at RHIC (particle production ratios, soft spectra, flows, and so on), observables specific for RHIC energies related to the Jet Quenching effect and Color Glass Condensate (CGC) manifestation are discussed. Preliminary results and specifics of particular experiments at RHIC are not considered.

Journal ArticleDOI
TL;DR: In this paper, the authors present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs ($2.7 3$ GeV/$c$) in $pp$, d+Au, and Au+AU collisions at $\snn=200$ Ge V.
Abstract: Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations of hadrons at forward rapidity with a mid-rapidity high-$\pt$ hadron, on the other hand, probe asymmetric partonic scatterings involving large-x quarks and small-x gluons. We present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs ($2.7 3$ GeV/$c$) in $pp$, d+Au, and Au+Au collisions at $\snn=200$ GeV. The implications of the results for small-x gluon distributions (Color Glass Condensate formation) and the energy loss of quark jets at forward rapidity in nuclear medium are discussed. %Their measurements in d+Au collisions, separately at the d-side and the Au-side, may be sensitive to Color Glass Condensate in the Au-nucleus. Their measurements in Au+Au collisions may probe quark-jet modification in nuclear medium.

Journal ArticleDOI
TL;DR: In this article, a series of three lectures on high energy scattering among hadrons in Quantum Chromodynamics is presented. Butler et al. describe the parton model, Bjorken scaling and the scaling violations due to the evolution of parton distributions with the transverse resolution scale.
Abstract: In this series of three lectures, we discuss several aspects of high energy scattering among hadrons in Quantum Chromodynamics. The first lecture is devoted to a description of the parton model, Bjorken scaling and the scaling violations due to the evolution of parton distributions with the transverse resolution scale. The second lecture describes parton evolution at small momentum fraction x, the phenomenon of gluon saturation and the Color Glass Condensate (CGC). In the third lecture, we present the application of the CGC to the study of high energy hadronic collisions, with emphasis on nucleus-nucleus collisions. In particular, we provide the outline of a proof of high energy factorization for inclusive gluon production.

Posted Content
TL;DR: In this paper, the photoproduction of quarkonium in coherent proton-proton and nucleus-nucleus interactions at the LHC was studied using the Color Glass Condensate (CGC) formalism, taking into account the parton saturation effects at high energies.
Abstract: In this contribution we study the photoproduction of quarkonium in coherent proton-proton and nucleus-nucleus interactions at the LHC. The integrated cross sections and rapidity distributions are estimated using the Color Glass Condensate (CGC) formalism, which takes into account the parton saturation effects at high energies. Nuclear shadowing effects are also taken into account.

Journal ArticleDOI
Fuqiang Wang1
TL;DR: In this paper, Zhao et al. present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs (2.7 3 GeV/c) in pp, d+Au, and Au-Au collisions at.
Abstract: Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations of hadrons at forward rapidity with a mid-rapidity high-p⊥ hadron, on the other hand, probe asymmetric partonic scatterings involving large-x quarks and small-x gluons. We present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs (2.7 3 GeV/c) in pp, d+Au, and Au+Au collisions at . The implications of the results for small-x gluon distributions (Color Glass Condensate formation) and the energy loss of quark jets at forward rapidity in nuclear medium are discussed.

Posted Content
TL;DR: In this paper, the predicted multiplicities in pp, pA and AA collisions at the LHC were predicted based on the Color Glass Condensate (CGC) approach.
Abstract: We present the predictions for hadron multiplicities in pp, pA and AA collisions at the LHC based on our approach to the Color Glass Condensate.