Narrow Results

Deep-elastic pp scattering at c.m. energy 14 TeV at LHC in the momentum transfer range 4 GeV² ≲ |t| ≲ 10 GeV² is planned to be measured by the TOTEM group. We study this process in a model where the deep-elastic scattering is due to a single hard collision of a valence quark from one proton with a valence quark from the other proton. The hard collision originates from the low-x gluon cloud around one valence quark interacting with that of the other. The low-x gluon cloud can be identified as color glass condensate and has size ≃0.3 F. Our prediction is that pp dσ/dt in the large |t| region decreases smoothly as momentum transfer increases. This is in contrast to the prediction of pp dσ/dt with visible oscillations and smaller cross sections by a large number of other models.

A global analysis of the latest diffractive deep inelastic scattering (DIS) data with gluon number fluctuations and impact parameter is performed. The impact parameter is introduced into the scattering amplitude by saturation scale with a Gaussian b-dependence. The results show that the description of the diffractive DIS data is improved once the gluon number fluctuations and impact parameter are included, with ${\chi }^2$/d.o.f = 0.878, ${\chi }^2$/d.o.f = 0.928 and ${\chi }^2$/d.o.f = 0.897 in different sets of free parameters. Moreover, we find that the impact parameter ($\lambda \simeq$ 0.1) is possibly compressed by the gluon number fluctuations, which leads to the value of saturation exponent returning to $\lambda \simeq$ 0.2. This outcome is compatible with the prediction that the saturation exponent is dominated by the fluctuations at sufficiently high energy, which may indicate the possibility of gluon number fluctuations in diffractive DIS data.

We review the color glass condensate effective theory, that describes the gluon content of a high energy hadron or nucleus, in the saturation regime. The emphasis is put on applications to high energy heavy ion collisions. After describing initial state factorization, we discuss the glasma phase, that precedes the formation of an equilibrated quark–gluon plasma. We end this review with a presentation of recent developments in the study of the isotropization and thermalization of the quark–gluon plasma.

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.

This is a review of applications of the Color Glass Condensate (CGC) 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.

The relativistic heavy-ion collider (RHIC) was constructed to achieve an asymptotic state of nuclear matter in heavy-ion collisions, a near-ideal gas of deconfined quarks and gluons denoted quark–gluon plasma or QGP. RHIC collisions are indeed very different from the hadronic processes observed at the Bevalac and AGS, but high-energy elementary-collision mechanisms are also non-hadronic. The two-component model (TCM) combines measured properties of elementary collisions with the Glauber eikonal model to provide an alternative asymptotic limit for A–A collisions. RHIC data have been interpreted to indicate formation of a strongly-coupled QGP (sQGP) or "perfect liquid". In this review, I consider the experimental evidence that seems to support such conclusions and alternative evidence that may conflict with those conclusions and suggest different interpretations.

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 wave function to the point where hydrodynamics may start becoming applicable.

The observation of long-range rapidity correlations among particles in high-multiplicity p–p and p–Pb collisions has created new opportunities for investigating novel high-density QCD phenomena in small colliding systems. We review experimental results related to the study of collective phenomena in small systems at RHIC and the LHC along with the related developments in theory and phenomenology. Perspectives on possible future directions for research are discussed with the aim of exploring emergent QCD phenomena.

We discuss some recent developments towards a quantitative understanding of the production and early-time evolution of bulk quark-gluon matter in ultrarelativistic heavy ion collisions.

Forward rapidity di-hadron azimuthal angular correlations in high energy proton-nucleus and proton-proton collisions are sensitive to quadrupoles; traceless correlator of 4 Wilson lines whereas single inclusive particle production iNVOLVES only dipoles, traceless correlator of 2 Wilson lines. We discuss the progress made in understanding the energy (rapidity) evolution of the quadrupole as well as its various limits.

We summarize the results of a recent first computation in the Color Glass Condensate effective field theory (CGC EFT) of the next-to-leading order (NLO) impact factor for inclusive photon+dijet production in electron-nucleus (e+A) deeply inelastic scattering (DIS) at small x. Our computation simultaneously provides the ingredients to compute fully inclusive DIS, inclusive photon, inclusive dijet and inclusive photon+jet channels to the same accuracy. We outline the Wilsonian renormalization group (RG) procedure by virtue of which extant results for the next-to-leading log (in x) JIMWLK evolution, can be integrated with our results to improve the precision to $O\left({\alpha }_s^3\ln \left(1/x\right)\right)$ accuracy. This paves the way towards quantitative studies of saturation at a future Electron-Ion Collider.

We review recent progress in NLO calculations for dilute-dense processes in the CGC picture. In particular, we focus here on recent steps in understanding high energy renormalization group evolution (BK/JIMWLK), the total DIS cross section at small x and forward particle production in proton-nucleus collisions at next-to-leading order.

We summarize our analytical and numerical results obtained up to now on CGC photon production at NLO in high energy hadronic collisions. This includes the full analytic NLO CGC formula based on which inclusive photon cross section is considered.

We investigate the dilepton production at backward rapidities in the dipole approach in pAu and pp collisions at RHIC and LHC energies. We analyze the nuclear modification ratio R_pA as a function of transverse momentum and rapidity. It is observed that this ratio is strongly related to the nuclear structure function ratio . We have found that the nuclear effects at large Bjorken x play an important role in the dilepton production at backward rapidities.

The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. The net baryon distributions and nuclear stopping power in the SPS and RHIC energy regions by taking advantage of the gluon saturation model are investigated. A new geometrical scaling variable is used to define the gluon saturation region of central rapidity of central nuclear collisions. Predications for net-baryon rapidity distributions and the mean rapidity loss in central Pb + Pb collisions at LHC are made in this paper.