We perform a numerical analysis of the two particle azimuthal correlations at central rapidities generated in $p$A collisions within the framework of the Color Glass Condensate. We extend the standard computations to include the subeikonal corrections which stem from considering the finite longitudinal width of the dense target. For practical reasons, we only consider the next-to-next-to-eikonal corrections instead of using the all-order expressions for the inclusive two gluon production cross section. We show that the subeikonal terms that we account for in the two gluon yields contribute to both even and odd harmonics, the latter being absent in the standard Color Glass Condensate calculations performed at eikonal accuracy. Our analysis confirms the vanishing of the subeikonal effects with increasing collision energy and when going to forward rapidities, as expected.
Azimuthal correlations of particles produced in nucleus-nucleus collisions at CERN SPS are discussed. The correlations quantified by the integral measure Phi are shown to be dominated by effects of collective flow.
We present a good description of recent experimental data on forward di-hadron azimuthal correlations measured in deuteron-gold collisions at RHIC, where monojet production has been observed. Our approach is based on the Color Glass Condensate effective theory for the small-x degrees of freedom of the nuclear wave function, including the use of non-linear evolution equations with running QCD coupling. Our analysis provides further evidence for the presence of saturation effects in RHIC data.
Recent experimental results have revealed a surprisingly rich structure of multiparticle azimuthal correlations in high energy proton-nucleus collisions. Final state collective effects can be responsible for many of the observed effects, but it has recently been argued that a part of these correlations are present already in the wavefunctions of the colliding particles. We evaluate the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. These would correspond to the fl…
We examine the origins of azimuthal correlations observed in high energy proton-nucleus collisions by considering the simple example of the scattering of uncorrelated partons off color fields in a large nucleus. We demonstrate how the physics of fluctuating color fields in the color glass condensate (CGC) effective theory generates these azimuthal multiparticle correlations and compute the corresponding Fourier coefficients v_n within different CGC approximation schemes. We discuss in detail the qualitative and quantitative differences between the different schemes. We will show how a recently…
The azimuthal elliptic asymmetry v2 observed in heavy ion collisions, is usually associated with properties of the medium created in the final state. We compute the azimuthal asymmetry which is due to multiple interactions of partons at the initial stage of nuclear collisions, and which is also present in $pA$ collisions. In our approach the main source of azimuthal asymmetry is the combination of parton multiple interactions with the steep variation of the nuclear density at the edge of nuclei. We apply the light-cone dipole formalism to compute the azimuthal asymmetry of prompt photons yield…
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…
We show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton-parton cross-section of $σ=1.5 - 3$ mb, naturally explains the long-range two-particle azimuthal correlation as observed in proton-proton and proton-nucleus collisions at the Large Hadron Collider.
We perform a numerical study of higher order saturation corrections to the dilute-dense approximation for multi-particle production in high-energy hadronic collisions in the framework of the Color Glass Condensate. We compare semi-analytical results obtained by performing a leading order expansion in the dilute field of the projectile with numerical simulations of the full Classical Yang-Mills dynamics for a number of phenomenologically relevant observables. By varying the saturation momentum of the target and the projectile, we establish the regime of validity of the dilute-dense approximatio…
Strong multiparticle azimuthal correlations have recently been observed in high energy proton-nucleus collisions. While final state collective effects can be responsible for many of the observations, the domain structure in the classical color field of a high energy nucleus also naturally leads to such correlations. We describe recent calculations of the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. We find significant differences between Wilson lines from the MV…
Confinement of a chromodynamical string can result in specific effects in scattering processes and multiparticle production. In particular, due to its rotation secondary fragments of the splitting apart string can move like stones thrown from a sling. That would be detected as the azimuthal asymmetry of particle distributions in individual events. Thus we propose to explain the elliptic flow observed in AA-collisions as a sling-effect. It can provide information about confinement of quarks inside particles or binding forces in nuclei. Nonclassical states of the created particles like the Schro…
We investigate the azimuthal asymmetry v2 of produced pions in pp and pA collisions at both RHIC and SPS energies. In our approach, based on the pQCD parton model and the light-cone QCD-dipole formalism, the azimuthal asymmetry results from a correlation between the color-dipole orientation and the impact parameter of the collision. We introduce the color-dipole orientation within an improved Born approximation and the saturation model which satisfies available DIS data, showing that the azimuthal asymmetry of partons and pions is very sensitive to the choice of the model, and that it is reduc…
We study nuclear dependences of azimuthal asymmetries in the Drell-Yan lepton pair production in nucleon-nucleus collisions with polarized nucleons.We use the "maximal two-gluon correlation approximation", so that we can relate the transverse momentum dependent quark distribution in a nucleus to that in a nucleon by a convolution with a Gaussian broadening.We use the Gaussian ansatz for the transverse momentum dependence of such quark distribution functions,and obtain the numerical results for the nuclear dependences.These results show that the averaged azimuthal asymmetries are suppressed.
Simple power counting arguments in the dilute-dense framework of the Color Glass Condensate (CGC) Effective Field Theory predict that even and odd azimuthal anisotropy harmonics of two-particle correlations in proton-nucleus collisions at the LHC will respectively satisfy v^2_{2n} ~ N_{ch}^0 and v^2_{2n+1} ~ N_{ch}, where N_{ch} denotes the number of charged particles. We show that these expectations are borne out qualitatively, and even quantitatively, within systematic uncertainties, for v_2 and v_4 in comparisons with data from the ATLAS collaboration. We also observe that ATLAS data for th…
We compute single inclusive hadron production in proton-proton and proton-nucleus collisions consistently within the CGC framework. The parameters in the calculations are obtained from electron-proton DIS and standard nuclear geometry. We obtain a good description of the DIS data without an anomalous dimension in the initial condition of the BK evolution and get a good agreement with the available single inclusive proton-proton and proton-nucleus data.
In this paper we calculate the contribution to rapidity and angular correlations of the first Pomeron loop diagram in the dense partonic environment. This diagram is expected to give the largest contribution to the density variation mechanism of the angular correlations. We show that this diagrams leads to sizable contributions to the rapidity correlation functions of the order of $σ_{in} /\Lb πR^2\Rb$ where $σ_{in}$ is the inelastic cross section and $R$ is the size of the typical dipole inside the proton saturation scale. Therefore, the correlations do not depend on the saturation scale. We …
We study DIS with a spin-1 hadron or a nucleus polarized in arbitrary direction. The differential cross-section in this case will have an azimuthal dependence. We derive the dependence by including contributions from twist-2- and twist-3 QCD operators. The twist-3 contribution is computed at tree-level. A spin-1 hadron or nucleus can have nonzero tensor polarization. We find that all structure functions related to the tensor-polarization of the initial hadron can be extracted by study the azimuthal dependence. A nonzero result of the structure functions of a nucleus from experiment will indica…
We consider dilepton production in high energy proton-nucleus (and very forward nucleus-nucleus) collisions. Treating the target nucleus as a Color Glass Condensate and describing the projectile proton (nucleus) as a collection of quarks and gluons as in the parton model, we calculate the differential cross section for dilepton production in quark-nucleus scattering and show that it is very sensitive to the saturation scale characterizing the target nucleus.
We use a Monte Carlo approach to study hadron azimuthal angular correlations in high energy proton-proton and central nucleus-nucleus collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energies at mid-rapidity. We build a hadron event generator that incorporates the production of $2\to 2$ and $2\to 3$ parton processes and their evolution into hadron states. For nucleus-nucleus collisions we include the effect of parton energy loss in the Quark-Gluon Plasma using a modified fragmentation function approach. In the presence of the medium, for the case when three partons are produced in …
We investigate the azimuthal anisotropy $v_2$ of particle production in nucleus-nucleus collisions in the maximum entropy approach. This necessitates two new phenomenological input parameters $δ$ and $λ_2$ compared with integrated multiplicity distributions. The parameter $δ$ describes the deformation of a flux tube and can be theoretically calculated in a bag model with a bag constant which depends on the density of surrounding flux tubes. The parameter $λ_2$ defines the anisotropy of the particle distribution in momentum space and can be connected to $δ$ via the uncertainty relation. In this…
The azimuthal anisotropies of the collective transverse flow of charged hadrons are investigated in a wide range of heavy-ion collision energies within the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which incorporates explicit partonic degrees-of-freedom in terms of strongly interacting quasiparticles (quarks and gluons) in line with an equation-of-state from lattice QCD as well as the dynamical hadronization and hadronic collision dynamics in the final reaction phase. The experimentally observed increase of the elliptic flow $v_2$ of charged hadrons with collision ene…
We show that particle production in proton-nucleus (pA) collisions in the Color Glass Condensate model can be related to Deep Inelastic Scattering of leptons on protons/nuclei (DIS). The common building block is the quark antiquark (or gluon-gluon) dipole cross section which is present in both DIS and pA processes. This correspondence in a sense generalizes the standard leading twist approach to pA collisions based on collinear factorization and perturbative QCD, and allows one to express the pA cross sections in terms of a universal quantity (dipole cross section) which, in principle, can be …
We perform an exploratory study of the role of coherent, medium-induced energy loss in azimuthal angular correlations in dihadron production in Deep Inelastic Scattering (DIS) at small $x$ where the target proton/nucleus is modeled as a Color Glass Condensate. In this approach coherent radiative energy loss is part of the higher order corrections to the leading order dihadron production cross section. We include the effects of both gluon saturation and coherent radiative energy loss and show that radiative cold-matter energy loss has a significant effect on the so-called coincidence probabilit…
We demonstrate that the striking systematics of two-particle azimuthal Fourier harmonics $v_2$ and $v_3$ in ultrarelativistic collisions of protons, deuterons and helium-3 ions off gold nuclei measured by the PHENIX Collaboration [arXiv:1805.02973] at the Relativistic Heavy Ion Collider (RHIC) is reproduced in the Color Glass Condensate (CGC) effective field theory. This contradicts the claim in [arXiv:1805.02973] that their data rules out initial state based explanations. The underlying systematics of the effect, as discussed previously in [arXiv:1705.00745,arXiv:1706.06260,arXiv:1801.09704],…
In the paper energy dependence of space-time extent of emission region obtained from Bose - Einstein correlations is studied for charged pions in various ion collisions for all experimentally available energies. There is no dramatic change of HBT parameters with increasing of collision energy per nucleon-nucleon pair, $\sqrt{s_{NN}}$, in domain of energies $\sqrt{s_{NN}} \geq 5$ GeV. Energy dependence of estimations for emission duration is almost flat for all energy domain under study within large error bars. Analytic function is suggested for smooth approximation of energy dependence of main…
We consider the influence of parton saturation in the Color Glass Condensate on the back-to-back azimuthal correlations of high $p_T$ hadrons in $pA$ (or $dA$) collisions. When both near--side and away--side hadrons are detected at mid-rapidity at RHIC energy, the effects of parton saturation are constrained to transverse momenta below the saturation scale $p_T \leq Q_s$; in this case the back-to-back correlations do not disappear but exhibit broadening. However when near-side and away-side hadrons are separated by several units of rapidity, quantum evolution effects lead to the depletion of b…
We discuss proton-nucleus collisions in the framework of the color glass condensate. By assuming that the proton can be described as a low density color source, we solve exactly the Yang-Mills equations corresponding to this type of collision, and then use this solution in order to calculate inclusive gluon production or quark-antiquark production. Our result shows that k_T-factorization, while valid for gluon production, is violated for quark pair production in proton-nucleus collisions.
We show how the limiting fragmentation phenomenon can arise from the Color Glass Condensate model of high energy QCD. We consider the very forward rapidity region in relativistic heavy ion collisions and argue that in this region, nucleus-nucleus collisions are similar to proton-nucleus collisions (up to shadowing corrections). We then use the known results for proton-nucleus cross sections to show that it leads to the phenomenon of limiting fragmentation in the very forward region of heavy ion collisions as observed at RHIC.
Color flux tubes (quark-gluon strings), formed at early stages of hadron-hadron collisions, may overlap in case of sufficiently high densities and interact, producing long-range azimuthal correlations. In the hypothesis of repulsive interaction, each string may acquire, before the hadronization, the additional transverse boost, which is an efficient sum of all accounted string-string interactions. This modifies transverse momenta to the particles formed in string decay, leading to modification of event-wise observables, like azimuthal asymmetry of two-particle correlations, over a wide range o…
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 HERA at small Bjorken-x, and the hadron multiplicities in nucleus-nucleus collisions at RHIC.
We study two-particle long-range rapidity correlations arising in the early stages of heavy ion collisions in the saturation/Color Glass Condensate framework, assuming for simplicity that one colliding nucleus is much larger than the other. We calculate the two-gluon production cross section while including all-order saturation effects in the heavy nucleus with the lowest-order rescattering in the lighter nucleus. We find four types of correlations in the two-gluon production cross section: (i) geometric correlations, (ii) HBT correlations accompanied by a back-to-back maximum, (iii) away-side…
We calculate azimuthal correlations in dAu collisions at different rapidities and centralities and argue that experimentally observed depletion of the back-to-back pick can be quantitatively explained by gluon saturation in the Color Glass Condensate of the Gold nucleus.
We perform a detailed comparison of long range rapidity correlations in the Color Glass Condensate framework to high multiplicity di-hadron data in proton-proton and proton-lead collisions from the CMS, ALICE and ATLAS experiments at the LHC. The overall good agreement thus far of the non-trivial systematics of theory with data is strongly suggestive of gluon saturation and the presence of subtle quantum interference effects between rapidity separated gluons. In particular, the yield of pairs collimated in their relative azimuthal angle $Δϕ\sim 0$, is sensitive to the shape of unintegrated glu…
RHIC experiments have recently measured the azimuthal correlation function of forward di-hadrons. The data show a disappearance of the away-side peak in central d+Au collisions, compared to p+p collisions, as was predicted by saturation physics. Indeed, we argue that this effect, absent at mid-rapidity, is a consequence of the small-x evolution into the saturation regime of the Gold nucleus wave function. We show that the data are well described in the Color Glass Condensate framework.
We derive 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. Both multiple scattering and non-linear QCD evolution at small-x are included. This is of relevance for measurements of two-particle correlations in the proton direction of proton-nucleus collisions at RHIC and LHC energies. The azimuthal angle distribution is peaked back to back and broadens as the momenta of the measured particles gets closer to the saturation scale.
We discuss azimuthal correlations in $dAu$ collisions at different rapidities and centralities and argue that experimentally observed depletion of the back-to-back peak can be quantitatively explained by gluon saturation in the Color Glass Condensate of the Gold nucleus.
The forthcoming LHC measurement of hadron multiplicity in proton-nucleus collisions is a crucial test of the k_t factorization and gluon saturation based models. Here, we provide quantitative predictions for the pseudorapidity distribution of charged particles produced in minimum bias proton-nucleus collisions at the LHC based on the idea of gluon saturation in the color-glass condensate framework. Our formulation gives good descriptions of the LHC and RHIC data for the charged-hadron multiplicities in both proton-proton and nucleus-nucleus collisions, and also the deep inelastic scattering at…
An overwhelming fraction of photons from relativistic heavy ion collisions has its origin in the decay of $π^0$ and $η$ mesons. We calculate the azimuthal asymmetry of the decay photons for several azimuthally asymmetric pion distributions. We find that the $k_T$ dependence of the elliptic flow parameter$v_2$ for the decay photons closely follows the elliptic flow parameter $v_2^{π^0}$ evaluated at $p_T \approx k_T+δ$, where $δ\approx$ 0.1 -- 0.2 GeV, for typical pion distributions measured in nucleus-nucleus collisions at relativistic energies. Similar results are obtained for photons from th…
We show that Bose-Einstein correlations of identical particles in hadron and nucleus high energy collisions, lead to long range rapidity correlations in the azimuthal angle. These correlations are inherent features of the CGC/saturation approach, however, their origin is more general than this approach. In framework of the proposed technique both even and odd $v_n$ occur naturally, independent of the type of target and projectile. We are of the opinion that it is premature to conclude that the appearance of azimuthal correlations are due to the hydrodynamical behaviour of the quark-gluon plasm…
This contribution discusses the phenomenon of parton saturation, the color glass picture of hadronic wavefuntions, and their relevance in the early stages of nucleus-nucleus collisions. Evidence for the color glass condensate in the presently available RHIC data is critically reviewed.
We analyze azimuthal anisotropy in heavy ion collisions related to the reaction plane in terms of standard reggeon approach and find that it is nonzero even when the final state interaction is switched off. This effect can be interpreted in terms of partonic structure of colliding nuclei. We use Feynman diagram analysis to describe details of this mechanism. Main qualitative features of the appropriate azimuthal correlations are discussed.
We study the azimuthal asymmetries for quark pair production in proton-nucleus collisions using a hybrid approach in which the nucleus is treated in the Color Glass Condensate (CGC) framework while the Lipatov approximation is applied on the proton side. Our treatment goes beyond the large N_c limit. We particularly focus on the so-called correlation limit where the imbalance of the transverse momentum of the quark pair is much smaller than the out-going individual quark transverse momenta. In this kinematic region, a matching between the hybrid approach and a factorization in terms of transve…
We compute two-particle production in p+A collisions and extract azimuthal harmonics, using the dilute-dense formalism in the Color Glass Condensate framework. The multiple scatterings of the partons inside the projectile proton on the dense gluons inside the target nucleus are expressed in terms of Wilson lines. They generate interesting correlations, which can be partly responsible for the signals of collectivity measured at RHIC and at the LHC. Most notably, while gluon Wilson loops yield vanishing odd harmonics, quark Wilson loops can generate sizable odd harmonics for two particle correla…
We compare the azimuthal correlations arising from three and two hadron production in high energy proton-proton and nucleus-nucleus collisions at \sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three and two-to-two parton-processes in perturbative QCD. We first compute the two and three hadron production cross sections in mid-rapidity proton-proton collisions. Then we consider Au + Au collisions including parton energy loss using the modified fragmentation function approach. By examining the geometrical paths the hard partons follow through the medium, we show that th…
The energy loss parameter $\hat q$ is one of the fundamental transport parameters of hadronic matter. Using the twist-4 collinear approach, we show that the $\cos ϕ$ azimuthal asymmetry in unpolarized semi-inclusive deeply inelastic scattering (SIDIS) off a large nucleus at intermediate transverse momentum is a sensitive observable for its determination. The effect is due to the suppression of the azimuthal asymmetry by final-state multiple scattering.
The azimuthal collimation of di-hadrons with large rapidity separations in high multiplicity p+p collisions at the LHC is described in the Color Glass Condensate (CGC) effective theory [1] by N_c^2 suppressed multi-ladder QCD diagrams that are enhanced α_S^(-8) due to gluon saturation in hadron wavefunctions. We show that quantitative computations in the CGC framework are in good agreement with data from the CMS experiment on per trigger di-hadron yields and predict further systematics of these yields with varying trigger pT and charged hadron multiplicity. Radial flow generated by re-scatteri…
Considering a dilute-dense situation suitable for pA collisions, we compute in the Color Glass Condensate the correlation between azimuthal asymmetries, specifically the squared second Fourier coefficient $v_2^2$, and the total multiplicity in the event. We also analyse the correlation between $v_2^2$ and the mean squared transverse momentum of particles in the event. In both cases, we find that the correlations are generally very small, consistent with the observations. We also note an interesting sharp change in the value of $v_2^2$ and its correlations as a function of the width of the tran…
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…
We calculate the differential cross section for the unpolarized semi-inclusive deeply inelastic scattering (SIDIS) process $e^-+N \to e^-+q+X$ in leading order (LO) of perturbative QCD and up to twist-4 in power corrections and study in particular the azimuthal asymmetry $<cos2ϕ>$. The final results are expressed in terms of transverse momentum dependent (TMD) parton matrix elements of the target nucleon up to twist-4. %Under the maximal two-gluon correlation approximation, these TMD parton matrix elements in a nucleus %can be expressed terms of a Gaussian convolution of that in a nucleon with…
We consider the J/Psi production in proton (deuteron) -- nucleus collisions at high energies. We argue that the production mechanism in this case is different from that in pp collisions due to gluon saturation in the nucleus and formation of the Color Glass Condensate. At forward rapidities (in the proton fragmentation region), the production of J/Psi is increasingly suppressed both as a function of rapidity and centrality. On the other hand, at backward rapidities at RHIC (in the fragmentation region of the nucleus) the coherent effects lead to a modest enhancement of the production cross sec…
In this paper we analytically extract the odd azimuthal anisotropy in the Classical Yang-Mills equations for the Glasma for pA collisions. We compute the first non-trivial term in the expansion of the proton sources of color charge. The computation is valid in the limit of a large nucleus when the produced particle momenta are larger than the saturation momentum of the proton.
We compute the production of quark-antiquark pairs in high energy collisions between a small and a large projectile, as in proton-nucleus collisions, in the framework of the Color Glass Condensate. We derive a general expression for quark pair-production, which is not k_t-factorizable. However, k_t-factorization is recovered in the limit of large mass pairs or large quark--anti-quark momenta. Our results are amenable to a simple interpretation and suggest how multi-parton correlations at small x can be quantified in high-energy proton/deuteron-nucleus collisions.
Multi-particle production in QCD is dominated by higher twist contributions. The operator product expansion is not very effective here because the number of relevant operators grow rapidly with increasing twist. The Color Glass Condensate (CGC) provides a framework in QCD to systematically discuss "classical" (multiple scattering) and "quantum" evolution (shadowing) effects in multi-particle production. The apparently insuperable problem of nucleus-nucleus scattering in QCD simplifies greatly in the CGC. A few examples are discussed with emphasis on open problems.
I give a pedagogical survey of the nuclear collective effects associated with gluon saturation and their impact on particle production in high-energy proton (or deuteron)-nucleus collisions at RHIC. At central rapidity, the theory predicts a Cronin peak due to independent multiple scattering off the valence quarks in the nucleus. At forward rapidities, the peak flattens out and disappears very fast, because of the correlations induced through quantum evolution in the nuclear gluon distribution at small x. Also, the ratio R_{pA} between the particle yield in proton-nucleus and proton-proton col…
We present a review of parton saturation/Color Glass Condensate physics in the context of deuteron-gold ($d+Au$) collisions at RHIC. Color Glass Condensate physics is a universal description of all high energy hadronic and nuclear interactions. It comprises classical (McLerran-Venugopalan model and Glauber-Mueller rescatterings) and quantum evolution (JIMWLK and BK equations) effects both in small-$x$ hadronic and nuclear wave functions and in the high energy scattering processes. Proton-nucleus (or $d+A$) collisions present a unique opportunity to study Color Glass Condensate predictions, sin…
The dilepton production is investigated in proton-nucleus collisions in the forward region using the Color Glass Condensate approach. The transverse momentum distribution ($p_T$), more precisely the low $p_T$ region, where the saturation effects are expected to increase, is analyzed. The ratio between proton-nucleus and proton-proton differential cross section for RHIC and LHC energies is evaluated, showing the effects of saturation at small $p_T$, and presenting a Cronin type peak at moderate $p_T$. These features indicate the dilepton as a most suitable probe to study the properties of the s…
We consider the single-inclusive minijet cross section in pA at forward rapidity within the Color Glass Condensate model of high energy collisions. We show that the nucleus appears black to the incident quarks except for very large impact parameters. A markedly flatter p_t distribution as compared to QCD in the dilute perturbative limit is predicted for transverse momenta about the saturation scale, which could be as large as Q_s^2 ~ 10 GeV^2 for a gold nucleus boosted to rapidity ~10 (as at the BNL-RHIC).
We calculate the inclusive small-x valence quark production cross section in proton-nucleus collisions at high energies. The calculation is performed in the framework of the Color Glass Condensate formalism. We consider both the case when the valence quark originates inside the nucleus and the case when it originates inside the proton. We first calculate the cross section in the quasi-classical approximation resumming the multiple rescatterings with the nucleus. Then we include the the effects of double logarithmic reggeon evolution and leading logarithmic gluon evolution in the obtained cross…
