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Register a new userImpact parameter profiles from nuclear shadowing ratio and applications to deuteron-gold collisions
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While current nuclear parton distribution functions (nPDFs) from global fits to experimental data are spatially homogeneous, many experimental observables in nucleus-nucleus collisions are presented in terms of centrality cuts. These cuts can be related to impact parameter using the Glauber theory and it is thus usual in the description of such observables to convolute an assumed impact parameter distribution with the homogeneous nPDFs. In this study we use the Gribov theory of nuclear shadowing supplemented with information from diffraction to model the impact parameter distributions of nuclear shadowing ratio in the small-$x$ region. The modeled distributions are applied to the description of the centrality dependence of observables in deuteron-gold (d+Au) collisions at $sqrt{s_{NN}} = 200$ AGeV.
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We calculate nuclear modification factors $R_{dAu}$, central-to-peripheral ratios, $R_{CP}$, and pseudorapidity asymmetries $Y_{Asym}$ in deuteron-gold collisions at $sqrt{s} = 200$ GeV in the framework of leading-order (LO) perturbative Quantum Chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS), the Frankfurt-Guzey-Strikman (FGS) and the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation functions in our calculations. Results are compared to experimental data from the BRAHMS and STAR collaborations.
In this work we present dipole scattering amplitudes, including the dependence on the impact-parameter, for a variety of nuclear targets of interest for the electron-ion colliders (EICs) being currently designed. These amplitudes are obtained by numerically solving the Balitsky-Kovchegov equation with the collinearly improved kernel. Two different cases are studied: initial conditions representing the nucleus under consideration and the solutions based on an initial condition representing a proton complemented by a Glauber-Gribov prescription to obtain dipole-nucleus amplitudes. We find that the energy evolution of these two approaches differ. We use the obtained dipole scattering amplitudes to predict ($i$) nuclear structure functions that can be measured in deep-inelastic scattering at EICs and ($ii$) nuclear suppression factors that reveal the energy evolution of shadowing for the different cases we studied. We compare our predictions with the available data.
We present a phenomenological approach (EPOS), based on the parton model, but going much beyond, and try to understand proton-proton and deuteron-gold collisions, in particular the transverse momentum results from all the four RHIC experiments. It turns out that elastic and inelastic parton ladder splitting is the key issue. Elastic splitting is in fact related to screening and saturation, but much more important is the inelastic contribution, being crucial to understand the data. We investigate in detail the rapidity dependence of nuclear effects, which is actually relatively weak in the model, in perfect agreement with the data, if the latter ones are interpreted correctly.
We argue that with an increase of the collision energy, elastic photoproduction of $rho$ mesons on nuclei becomes affected by the significant cross section of photon inelastic diffraction into large masses, which results in the sizable inelastic nuclear shadowing correction to $sigma_{gamma A to rho A}$ and the reduced effective $rho$-nucleon cross section. We take these effects into account by combining the vector meson dominance model, which we upgrade to include the contribution of high-mass fluctuations of the photon according to QCD constraints, and the Gribov-Glauber approximation for nuclear shadowing, where the inelastic nuclear shadowing is included by means of cross section fluctuations. The resulting approach allows us to successfully describe the data on elastic $rho$ photoproduction on nuclei in heavy ion UPCs in the $7 {rm GeV} < W_{gamma p} < 46$ GeV energy range and to predict the value of the cross section of coherent $rho$ photoproduction in Pb-Pb UPCs at $sqrt{s_{NN}}=5.02$ TeV in Run 2 at the LHC, $dsigma_{Pb Pb to rho Pb Pb} (y=0)/dy= 560 pm 25$ mb.
We study the impact parameter dependence of inelasticity in the framework of an updated geometrical model for multiplicity distribution. A formula in which the inelasticity is related to the eikonal is obtained. This framework permits a calculation of the multiplicity distributions as well as the inelasticity once the eikonal function is given. Adopting a QCD inspired parametrization for the eikonal, in which the gluon-gluon contribution dominates at high energy and determines the asymptotic behavior of the cross sections, we find that the inelasticity decreases as collision energy is increased. Our results predict the KNO scaling violation observed at LHC energies by CMS Collaboration.
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