569 research outputs found

    NLO Corrections to Deeply-Virtual Compton Scattering

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    We have calculated the NLO corrections to the twist-2 part of the deeply-virtual Compton scattering amplitude. Our results for the transverse and antisymmetric parts agree with recent calculations by Ji and Osborne and by Belitsky and M\"uller. In addition we present NLO results for the longitudinal part of the amplitude.Comment: 8 pages, Latex. Error in polarised gluonic coefficient in Eq.(8) correcte

    Universality for 2D Wedge Wetting

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    We study 2D wedge wetting using a continuum interfacial Hamiltonian model which is solved by transfer-matrix methods. For arbitrary binding potentials, we are able to exactly calculate the wedge free-energy and interface height distribution function and, thus, can completely classify all types of critical behaviour. We show that critical filling is characterized by strongly universal fluctuation dominated critical exponents, whilst complete filling is determined by the geometry rather than fluctuation effects. Related phenomena for interface depinning from defect lines in the bulk are also considered.Comment: 4 pages, 1 figur

    Quark model predictions for the SU(6)-breaking ratio of the proton momentum distributions

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    The ratio between the anomalous magnetic moments of proton and neutron has been recently parametrized by the ratio of proton momentum fractions M2qvalM_{2}^{q_{val}}. This ratio is evaluated using different constituent quark models, starting from the CQM density distributions and calculating the next-to leading order distributions. We show that this momentum fractions M2qvalM_{2}^{q_{val}} ratio is a sensitive test for SU(6)-breaking effects and therefore it is useful to distinguish among different CQMs. We investigate also the possibility of getting constraints on the formulation of quark structure models.Comment: 12 pages, 3 figure

    Ethnic In-Group Favoritism Among Minority and Majority Groups: Testing the Self-Esteem Hypothesis Among Preadolescents

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    The self-esteem hypothesis in intergroup relations, as proposed by social identity theory (SIT), states that successful intergroup discrimination enhances momentary collective self-esteem. This hypothesis is a source of continuing controversy. Furthermore, although SIT is increasingly used to account for children’s group attitudes, few studies have examined the hypothesis among children. In addition, the hypothesis’s generality makes it important to study among children from different ethnic groups. The present study, conducted among Dutch and Turkish preadolescents, examined momentary collective self-feelings as a consequence of ethnic group evaluations. The results tended to support the self-esteem hypothesis. In-group favoritism was found to have a self-enhancing effect among participants high in ethnic identification. This result was found for ethnic majority (Dutch) and minority (Turkish) participants.

    Nonperturbative versus perturbative effects in generalized parton distributions

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    Generalized parton distributions (GPDs) are studied at the hadronic (nonperturbative) scale within different assumptions based on a relativistic constituent quark model. In particular, by means of a meson-cloud model we investigate the role of nonperturbative antiquark degrees of freedom and the valence quark contribution. A QCD evolution of the obtained GPDs is used to add perturbative effects and to investigate the GPDs' sensitivity to the nonperturbative ingredients of the calculation at larger (experimental) scale.Comment: 17 pages, 10 figures; submitted to Phys. Rev.
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