Probing the partonic structure of pentaquarks in hard electroproduction

Exclusive electroproduction of a K or K"* meson on the nucleon can give a #THETA#"+ pentaquark in the final state. This reaction offers an opportunity to investigate the structure of pentaquark baryons at parton level. We discuss the generalized parton distributions for the N #-># #THETA#"+ transition and give the leading order amplitude for electroproduction in the Bjorken regime. Different production channels contain complementary information about the distribution of partons in a pentaquark compared with their distribution in the nucleon. Measurement of these processes may thus provide deeper insight into the very nature of pentaquarks. (orig.)Available from TIB Hannover: RA 2999(03-200) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Symmetry properties of the effective action for high-energy scattering in QCD

We study the effective action describing high-energy scattering processes in the multi-Regge limit of QCD, which should provide the starting point for a new attempt to overcome the limitations of the leading logarithmic and the eikonal approximations. The action can be obtained via simple graphical rules or by integrating in the QCD functional integral over momentum modes of gluon and quark fields that do not appear explicitiley as scattering or exchanged particles in the considered processes. The supersymmetry is used to obtain the terms in the action involving quark fields from the pure gluonic ones. We observe a Weizsaecker - Williams type relation between terms describing scattering and production of particles. (orig.)Available from TIB Hannover: RA 2999(94-064) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Diffractive meson production from virtual photons with odd charge-parity exchange

We calculate the cross section of diffractive charge-parity C=+1 neutral meson production in virtual photon proton collision at high energies. Due to the opposite C-parities of photon and meson M"+ (M"+=#eta#_c, #pi#"0, a_2) this process probes the t-channel C=-1 odderon exchange which is described here as noninteracting three-gluon exchange. Estimates for the cross section of inelastic diffractive process #gamma#"*p #-># #eta#_cX_p are presented. The total cross section of diffractive #eta#_c meson photoproduction is found to be 47 pb. The cross sections for the diffractive production of light mesons (#pi#"0, a_2) in #gamma#"*p collisions are of the same order if the photon virtuality Q"2 is m"2_c. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman