Reggeon and pion contributions in semi-exclusive diffractive processes at HERA

A detailed analysis of semi-exclusive diffractive processes in e-p DIS at HERA, with the diffractive final states in the forward direction is presented. The contributions of the subleading f_2, \omega, a_2, \rho reggeons and the pion exchanges to the diffractive structure function with the forward proton or neutron are estimated. It is found that the (a_2,\rho) reggeons are entirely responsible for the forward neutron production at x_P < 10^{-3}. The \pi N production in the forward region is estimated using the Deck mechanism. The significance of this reaction for the processes measured at HERA, especially with the leading neutron, is discussed.Comment: Strongly revised version accepted for publication in Phys.Rev.D. Latex, 14 pages with 5 eps figures include

On the Flavor Structure of the Constituent Quark

We discuss the dressing of constituent quarks with a pseudoscalar meson cloud within the effective chiral quark model. SU(3) flavor symmetry breaking effects are included explicitly. Our results are compared with those of the traditional meson cloud approach in which pions are coupled to the nucleon. The pionic dressing of the constituent quarks explains the experimentally observed violation of the Gottfried Sum Rule and leads to an enhanced nonperturbative sea of quark-antiquark pairs in the constituent quark and consequently in the nucleon. We find 2.5 times more pions and 10-15 times more kaons in the nucleon than in the traditional picture.Comment: 7 pages, LaTeX, 4 Postscript figures, to appear in J. Phys.

Energy Dependence of the Contribution of Pion Exchange to Large-Rapidity-Gap Events in Deep Inelastic Scattering

We study the energy dependence of the contribution of pion exchange to large-rapidity-gap events in deep inelastic scattering. The results show that this contribution can be quite significant at low energy and that the LRG events observed by E665 collaboration in \mu Xe and \mu D interactions at 490 $GeV$ can be reasonably well described in terms of meson exchange. We also show that the distribution of the maximum rapidity for all hadrons is quite different from that for charged hadrons only and that the former exhibits also shoulder-like structure for events at 490 $GeV$ similar to that at HERA.Comment: 12 pages, 4 figures, Phys. Rev. D (in press

Antidepressants and inflammatory bowel disease: a systematic review

BACKGROUND: A number of studies have suggested a link between the patient's psyche and the course of inflammatory bowel disease (IBD). Although pharmacotherapy with antidepressants has not been widely explored, some investigators have proposed that treating psychological co-morbidities with antidepressants may help to control disease activity. To date a systematic analysis of the available studies assessing the efficacy of antidepressants for the control of somatic symptoms in IBD patients has not been performed. METHODS: We searched electronic databases, without any language restriction. All relevant papers issued after 1990 were examined. RESULTS: 12 relevant publications were identified. All of them referred to non-randomised studies. Antidepressants reported in these publications included paroxetine, bupropion, amitriptyline, phenelzine, and mirtazapine. In 10 articles, paroxetine, bupropion, and phenelzine were suggested to be effective for treating both psychological and somatic symptoms in patients suffering from IBD. Amitriptyline was found ineffective for treating somatic symptoms of IBD. Mirtazapine was not recommended for IBD patients. CONCLUSION: Although most of reviewed papers suggest a beneficial effect of treatment with antidepressants in patients with IBD, due to the lack of reliable data, it is impossible to judge the efficacy of antidepressants in IBD. Properly designed trials are justified and needed based upon the available uncontrolled data

Nonperturbative versus perturbative effects in generalized parton distributions

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.

Pion and Rho Structure Functions from Lattice QCD

We calculate the lower moments of the deep-inelastic structure functions of the pion and the rho meson on the lattice. Of particular interest to us are the spin-dependent structure functions of the rho. The calculations are done with Wilson fermions and for three values of the quark mass, so that we can perform an extrapolation to the chiral limit.Comment: 30pp, LaTeX2e with 15 eps figures using epsfig. Postscript file also available from ftp://ftp.th.physik.uni-frankfurt.de/pub/cbest/pionrho.ps or http://www.th.physik.uni-frankfurt.de/~cbest/pionrho.p

Leptogenesis via multiscalar coherent evolution with supersymmetric neutrino see-saw

A novel scenario of leptogenesis is investigated in the supersymmetric neutrino see-saw model. The right-handed sneutrino ${\tilde N}$ and the $\phi$ field in the ${\tilde L} H_u$ direction of the slepton and Higgs doublets start together coherent evolution after the inflation with right-handed neutrino mass $M_N$ smaller than the Hubble parameter of inflation. Then, after some period the motion of ${\tilde N}$ and $\phi$ is drastically changed by the cross coupling $M_N h_\nu {\tilde N}^* \phi \phi$ from the $M_N N N$ and $h_\nu N L H_u$ terms, and the significant asymmetries of ${\tilde N}$ and ${\tilde L}$ are generated. The ${\tilde L}$ asymmetry is fixed later by the thermal effect as the lepton number asymmetry for baryogenesis, while the ${\tilde N}$ asymmetry disappears through the decays ${\tilde N} \to {\bar L} {\bar{\tilde H}}_u, {\tilde L} H_u$ with almost the same rate but opposite final lepton numbers.Comment: 4pages, 1 figure; submitted to Physical Review D. The renormalization group effects were include