The AGL Equation from a Dipole Picture

The AGL equation includes all multiple pomeron exchanges in the double logarithmic approximation (DLA) limit, leading to an unitarized gluon distribution in the small $x$ regime. This equation was originally obtained using the Glauber-Mueller approach. We demonstrate in this contribution that the AGL equation can also be obtained from the dipole picture. Our conclusion is that the AGL equation is a good candidate for an unitarized evolution equation at small $x$ in the DLA limit.Comment: 3 pages. To be published in the proceedings of 7th International Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, Germany, 19 - 23 Apr 199

Seeking the Shadowing in eA Processes

We consider the behavior of the slope of the nuclear structure function $F_2^A$ in the kinematic region which will be explored in the eA HERA collider. We demonstrate that, similarly to the nucleon case, a `turn over' is predicted in this observable. Moreover, we predict that the presence of the shadowing corrections implies that the maximum value of the slope is dependent of the number of nucleons A, differently from the DGLAP predictions. Our conclusion is that the measurement of this observable will allow to evidentiate the presence of the shadowing corrections.Comment: 10 pages, 1 figur

Searching Saturation in eA Processes

The high density effects should be manifest at small x and/or large nuclei. In this letter we consider the behavior of nuclear structure function $F_2^A$ slope in the kinematic region which could be explored in the future eA colliders as a search of these effects. We verify that the high density implies that the maximum value of the slope occurs at large values of the photon virtuality, i.e. in a perturbative regime, and is dependent of the number of nucleons A and energy. Our conclusion is that the measurement of this observable will allow to explicit the saturation.Comment: 13 pages, 2 figures, 1 tabl

Quarkonium+γ\gamma production in coherent hadron - hadron interactions at LHC energies

In this paper we study the $H + \gamma$ ($H = J/\Psi$ and $\Upsilon$) production in coherent hadron - hadron interactions at LHC energies. Considering the ultrarelativistic protons as a source of photons, we estimate the $\gamma + p \rightarrow H + \gamma + X$ cross section using the non-relativistic QCD (NRQCD) factorization formalism and considering different sets of values for the matrix elements. Our results for the total $p + p \rightarrow p + H + \gamma + X$ cross sections and rapidity distributions at $\sqrt{s} = 7$ and 14 TeV demonstrate that the experimental analysis of the $J/\Psi + \gamma$ production at LHC is feasible.Comment: 6 pages, 3 figures, 1 table. Improved version with a new figure. Version to be published in European Physical Journal

The Description of F2F_2 at Very High Parton Densities

The behavior of the structure function at high energies (high densities) is directly associated to the gluon distribution. In this paper we analyze the asymptotic behavior of the structure function at very high densities considering a leading and a higher twist relation between these two quantities. We verify that (a) if the leading twist relation between the structure function and the gluon distribution is used, we recover the black disc limit, and (b) a softer behavior is predicted if a higher twist relation between $F_2$ and $xG$ is considered. While the first behavior is well-established by the current high density approaches, the higher twist behavior is a new result. In both cases, the $F_2$ structure function unitarizes and the Froissart boundary is not violated in the asymptotic regime of high density QCD.Comment: 14 pages. Accepted for publication in Physics Letters

Constraining the free parameter of the high parton density effects

The high density parton effects are strongly dependent of the spatial gluon distribution within the proton, with radius $R$, which cannot be derived from perturbative QCD. In this paper we assume that the unitarity corrections are present in the HERA kinematical region and constrain the value of $R$ using the data for the proton structure function and its slope. We obtain that the gluons are not distributed uniformly in the whole proton disc, but behave as concentrated in smaller regions.Comment: 16 pages, 5 figure

Charm production in diffractive deep inelastic scattering

The diffractive open charm production is computed in perturbative QCD formalism and in the Regge approach. The results are compared with recent data on charm diffractive structure function measured at DESY-HERA. Our results demonstrate that this observable can be useful to discriminate the QCD dynamics.Comment: LaTeX, 13 pages, 2 figures. Version to be published in Phys. Lett.

Unitarity Corrections to the Proton Structure Functions through the Dipole Picture

We study the dipole picture for the description of the deep inelastic scattering, focusing on the structure functions which are driven directly by the gluon distribution. One performs estimates using the effective dipole cross section given by the Glauber-Mueller approach in QCD, which encodes the corrections due to the unitarity effects associated with the saturation phenomenon. We also address issues about frame invariance of the calculations when analysing the observables.Comment: 16 pages, 8 figures. Version to be published in Phys. Rev.

Constraining the nuclear gluon distribution in eAeA processes at RHIC

A systematic determination of the gluon distribution is of fundamental interest in understanding the parton structure of nuclei and the QCD dynamics. Currently, the behavior of this distribution at small $x$ (high energy) is completely undefined. In this paper we analyze the possibility of constraining the nuclear effects present in $xg^A$ using the inclusive observables which would be measured in the future electron-nucleus collider at RHIC. We demonstrate that the study of nuclear longitudinal and charm structure functions allows to estimate the magnitude of shadowing and antishadowing effects in the nuclear gluon distribution.Comment: 6 pages, 3 eps figure

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results