Geometric scaling in ultrahigh energy neutrinos and nonlinear perturbative QCD

The ultrahigh energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviors for its magnitude for ultrahigh energies. In this contribution is presented a summary of current predictions based on the non-linear QCD evolution equations, the so-called perturbative saturation physics. In particular, predictions are shown based on the parton saturation approaches and the consequences of geometric scaling property at high energies are discussed. The scaling property allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization.Comment: 6 pages, one figure. Presented at First Caribbean Symposium on Nuclear and Astroparticle Physics - STARS2011, La Habana, Cuba, 2011. arXiv admin note: substantial text overlap with arXiv:1011.2718 by different author

Double -- photon exclusive processes with heavy quark -- heavy antiquark pairs in high-energy Pb-Pb collisions at LHC

The cross section for exclusive heavy quark and heavy antiquark pair ($Q \bar Q$) production in peripheral ultrarelativistic heavy ion collisions is calculated for the LHC energy $\sqrt{s_{NN}}$ = 5.5 TeV. Here we consider only processes with photon--photon interactions and omit diffractive contributions. We present results in the impact parameter equivalent photon approximation (EPA) and compare some of them with results obtained by exact calculations of the Feynman diagrams in the momentum space. We include both $Q \bar Q$, $Q \bar Q g$ and $Q \bar Q q \bar q$ final states as well as photon single-resolved components. Realistic charge densities in nuclei were taken in the calculation. The different components give contributions of the same order of magnitude to the nuclear cross section. The cross sections found here are smaller than those for the diffractive photon-pomeron mechanism and larger than diffractive pomeron-pomeron discussed in the literature.Comment: 12 pages, 9 figures, 5 table

Geometric scaling in ultrahigh energy neutrinos and nonlinear perturbative QCD

It is shown that in ultrahigh energy inelastic neutrino-nucleon(nucleus) scattering the cross sections for the boson-hadron(nucleus) reactions should exhibit geometric scaling on the single variable tau_A =Q2/Q2_{sat,A}. The dependence on energy and atomic number of the charged/neutral current cross sections are encoded in the saturation momentum Q_{sat,A}. This fact allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization based on the scaling property.Comment: 5 pages, 4 figure

Investigating Fl (x, Q2) at fixed energy in the color dipole formalism

At small x, the structure function FL(x,Q2) is driven by the gluon content of the nucleon target and consequently it can unravel the underlying QCD dynamics in that region. In this work, one studies its behavior on the photon virtuality Q2 at fixed energy within the color dipole formalism for models considering parton saturation effects. The reason is that they resum a wide class of higher-twist contributions, which have an important influence on the FL description towards low Q2. It is shown that the geometric scaling property holds for the longitudinal cross section. Moreover, the effective anomalous dimension in the scaling dipole cross sections can be investigated by studing both the turn-over and the large Q2 regions of the recent experimental measurements

High energy DVCS on a photon and related meson exclusive production

In this work we estimate the differential cross section for the high energy deeply virtual Compton scattering on a photon target within the QCD dipole-dipole scattering formalism. For the phenomenology, a saturation model for the dipole-dipole cross section for two photon scattering is considered. Its robustness is supported by good description of current accelerator data. In addition, we consider the related exclusive vector meson production processes. This analysis is focused on the light $\rho$ and $\phi$ meson production, which produce larger cross sections. The phenomenological results are compared with the theoretical calculation using the CD BFKL approach.Comment: 6 pages, 5 figures. Version to be published in Physical Review

Investigating the QCD dynamical entropy in high-energy hadronic collisions

The dynamical entropy of dense gluonic states in proton-proton collisions at high energies is studied by using phenomenological models for the unintegrated gluon distribution. The corresponding transverse momentum probability distributions are evaluated in terms of rapidity. The dynamical entropy density is obtained in the rapidity range relevant for the collisions at the Large Hadron Collider. The total entropy density for the dense system is computed as a function of the rapidity evolution ΔY ¼ Y − Y0 given an initial rapidity Y0. The theoretical uncertainties are investigated, and a comparison with related approaches in literature is done

Hard gluon evolution in warming medium

We describe the energy distribution of hard gluons travelling through a dense quark–gluon plasma whose temperature increases linearly with time, within a probabilis tic perturbative approach. The results were applied to the thermalization problem in heavy ion collisions. In the weak coupling picture this thermalization occurs from “the bot tom up”: high energy partons, formed early in the collision, radiate low energy gluons which then proceed to equilibrate among themselves, forming a thermal bath that brings the high energy sector to equilibrium. We see that, in this sce nario, the dynamic we describe must set in around t ∼ 0.5 fm/c after the collision in order to reach a fully thermalized state at t ∼ 1 fm/c. We then look at the entropy density and average temperature of the soft thermal bath, as the system approaches (local) thermal equilibrium

Investigating entanglement entropy at small x in DIS off protons and nuclei

In this work we analyze the entanglement entropy in deep inelastic scattering off protons and nuclei. It is computed based on the formalism where the partonic state at small-x is maximally entangled with proton being constituted by large number of microstates occurring with equal probabilities. We consider analytical expressions for the number of gluons, Ngluon, obtained from gluon saturation models for the dipole-target amplitudes within the QCD color dipole picture. In particular, the nuclear entanglement entropy per nucleon is studied. We also study the underlying uncertainties on these calculations and compare the results to similar investigations in literature