Energy versus centrality dependence of the jet quenching parameter q̂ at RHIC and LHC: a new puzzle?

The central goal of jet quenching studies in high-energy nuclear collisions is the characterization of those QCD medium properties that are accessible by these probes. Most of the discussion in the last years has been focused on the determination of the jet quenching parameter, q^ . We present here an extraction of this parameter using data of inclusive particle suppression at RHIC and LHC energies for different centralities. Our approach consists in fitting a K factor that quantifies the departure of this parameter from an ideal estimate, K≡q^/(2ϵ3/4)K≡q^/(2ϵ3/4) , where q^q^ is determined by the local medium quantities as provided by hydrodynamical calculations. We find that this K factor is larger at RHIC than at the LHC, as obtained already in previous analyses, but, surprisingly, it is almost independent of the centrality of the collision. Taken at face value, the K factor would not depend on the local properties of the medium as energy density or temperature, but on global collision quantities such as the center of mass energy. This is a very intriguing, unexpected possibility for which we cannot yet provide a clear interpretation. We also comment on the limitations of the formalism that may affect this conclusionThis research was supported by the European Research Council Grant HotLHC ERC2011-StG-279579; the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/under REA Grant Agreement #318921 (NA); Ministerio de Ciencia e Innovación of Spain under project FPA2014-58293-C2-1-P; Xunta de Galicia (Consellería de Educación)—the group is part of the Strategic Unit AGRUP2015/11. C. Andrés thanks the Spanish Ministery of Education, Culture and Sports for financial support (Grant FPU2013- 03558)S

Hadroproduction in nuclear media

En el presente trabajo estudiamos las modificaciones generadas por la presencia de medios nucleares en los estados inicial y final de procesos que involucran hadrones. Realizamos el análisis en el contexto de QCD a segundo orden en el desarrollo perturbativo. Para ello efectuamos una descripción exhaustiva de la cinemática de procesos de dispersión inelástica profunda y colisiones hadrónicas en el vacío. A partir de esto analizamos la incidencia de los medios nucleares sobre la distribución de partones en nucleones ligados. Dicho estudio incluye una actualización de los análisis realizados hasta el momento, a saber la inclusión de efectos de masa por la presencia de quarks pesados, el agregado de nuevos resultados experimentales y el impacto de las modificaciones en las funciones de fragmentación debidas a la presencia del medio nuclear. Por otro lado investigamos también las modificaciones de estado final observadas por los experimentos de DESY y RHIC, y presentamos funciones de fragmentación nucleares, extraidas en forma consistente con la determinación de distribuciones partónicas. Empleando estos resultados, brindamos predicciones para experimentos a realizarse en el LHC, y en los futuros LHeC y EIC.In the present thesis we study the modification of initial and final hadronic states when the processes occur in nuclear media. We make this analysis in the context of QCD at next-to-leading order in the perturbation series. We present a thorough description of the kinematics of deep-inelastic scattering and hadronic collisions in vacuum. From this point we analyze the partonic distribution functions on bounded nuclei. There we consider all the characteristics of up-to-date analysis, such as heavy quarks mass effects and new experimental results. We also take into account the novel set of nuclear fragmentation functions in order to get a good description of single-inclusive hadron production in proton(deuteron)-nucleus collisions. On the other hand we also study the final state modification observed by the HERMES collaboration at DESY and by the four collaborations at RHIC, and present the first set of nuclear fragmentation functions, which we extract in a consistent way. Using these results, we present predictions for experiments at LHC and future colliders LHeC and EIC.Fil:Zurita, María Pía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Producción de hadrones en medios nucleares

En el presente trabajo estudiamos las modificaciones generadas por la presencia de medios nucleares en los estados inicial y final de procesos que involucran hadrones. Realizamos el análisis en el contexto de QCD a segundo orden en el desarrollo perturbativo. Para ello efectuamos una descripción exhaustiva de la cinemática de procesos de dispersión inelástica profunda y colisiones hadrónicas en el vacío. A partir de esto analizamos la incidencia de los medios nucleares sobre la distribución de partones en nucleones ligados. Dicho estudio incluye una actualización de los análisis realizados hasta el momento, a saber la inclusión de efectos de masa por la presencia de quarks pesados, el agregado de nuevos resultados experimentales y el impacto de las modificaciones en las funciones de fragmentación debidas a la presencia del medio nuclear. Por otro lado investigamos también las modificaciones de estado final observadas por los experimentos de DESY y RHIC, y presentamos funciones de fragmentación nucleares, extraidas en forma consistente con la determinación de distribuciones partónicas. Empleando estos resultados, brindamos predicciones para experimentos a realizarse en el LHC, y en los futuros LHeC y EIC

Global analysis of nuclear parton distributions

We present a new global QCD analysis of nuclear parton distribution functions and their uncertainties. In addition to the most commonly analyzed data sets for the deep-inelastic scattering of charged leptons off nuclei and Drell-Yan dilepton production, we include also measurements for neutrino-nucleus scattering and inclusive pion production in deuteron-gold collisions. The analysis is performed at next-to-leading order accuracy in perturbative QCD in a general mass variable flavor number scheme, adopting a current set of free nucleon parton distribution functions, defined accordingly, as reference. The emerging picture is one of consistency, where universal nuclear modification factors for each parton flavor reproduce the main features of all data without any significant tension among the different sets. We use the Hessian method to estimate the uncertainties of the obtained nuclear modification factors and examine critically their range of validity in view of the sparse kinematic coverage of the present data. We briefly present several applications of our nuclear parton densities in hard nuclear reactions at BNL-RHIC, CERN-LHC, and a future electron-ion collider. © 2012 American Physical Society.Fil: de Florian, Daniel Enrique. Universidad de Buenos Aires; Argentina. University Of Zurich, Institute For Theoretical Physics; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Sassot, Rodolfo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Zurita, María Pía. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Stratmann, Marco. Brookhaven National Laboratory; Estados Unido

Impact of HIV-ART on the restoration of Th17 and Treg cells in blood and female genital mucosa

Abstract The aim of this study was to evaluate the effectiveness of antiretroviral treatment (ART) on the proportion and functions of Th17 and Treg cells in peripheral blood and female genital tract (FGT) respectively. To this aim, samples from 41 HIV-neg, 33 HIV+ ART-naïve and 32 HIV+ ART+ subjects were obtained. In peripheral blood, altered Th17 and Th17/Treg proportions were normalized in HIV+ ART+, but certain abnormal Treg and activated T-cell proportions were still observed. In FGT, abnormal patterns of secretion for Th17-related cytokines were observed in cervical mononuclear cells (CMCs) from HIV+ women, even in those from HIV+ ART+, compared to the HIV-neg group. Moreover, these altered patterns of secretion were associated with diminished levels of CXCL5 and CXCL1 chemokines and with an immunoregulatory skew in the CCL17/CCL20 ratio in ectocervix samples of these women. Finally, ART did not restore proportions of Th17-precursor cells with gut-homing potential in PBMCs, and positive correlations between these cells and the levels of IL-17F and IL-21 production by CMCs may suggest that a better homing of these cells to the intestine could also imply a better restoration of these cells in the female genital tract. These results indicate that antiretroviral treatment did not restore Th17-related immune functions completely at the female mucosal level