Bethe-Salpeter Amplitudes and Static Properties of the Deuteron

Extended calculations of the deuteron's static properties, based on the numerical solution of the Bethe-Salpeter equation, are presented. A formalism is developed, which provides a comparative analysis of the covariant amplitudes in various representations and nonrelativistic wave functions. The magnetic and quadrupole moments of the deuteron are calculated in the Bethe-Salpeter formalism and the role of relativistic corrections is discussed.Comment: 33 pages ([aps]{revtex} style), 9 Postscript figures; (55 pages if [preprint,aps]{revtex} style is used

Induced hypermultiplet self-interactions in N=2 gauge theories

We calculate the charged hypermultiplet low-energy effective action in the Coulomb branch of the 4D, N = 2 gauge theory, by using the harmonic superspace approach. We find that the unique leading contribution is given by the harmonic-analytic Lagrangian of the fourth order in the hypermultiplet superfields, with the induced coupling constant being proportional to central charges of N = 2 SUSY algebra. The central charges are identified with Cartan generators of the internal symmetry, and they give BPS masses to the hypermultiplets. The induced hyper-Kaehler metrics appear to be the Taub-NUT metric or its higher-dimensional generalizations. Simultaneously, non-trivial scalar potentials are produced. Within the harmonic superspace method, we show an equivalence between the two known approaches to the 4D central charges. In the first one, the central charges are obtained via the Scherk-Schwarz dimensional reduction from six dimensions, whereas in the second one they are generated by a covariantly-constant background gauge superfield. The more general situation, when N = 2 SUSY is spontaneously broken by Fayet-Iliopoulos (FI) terms, is also considered. We argue that the induced Taub-NUT self-coupling is stable against adding the FI terms. Possible non-perturbative generalizations of the induced hypermultiplet self-interactions are discussed. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Polarization observables in the reaction NN #-># NN#phi#

We study the reaction NN #-># NN#PHI# slightly above the threshold within an extended one-boson exchange model which also accounts for uud knock-out. It is shown that polarization observables, like the beam-target asymmetry, are sensible quantities for identifying a ss admixture in the nucleon wave function on the few per cent level. (orig.)25 refs.Available from TIB Hannover: RR 1847(202) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

DGLAP and BFKL evolution equations in the N=4 supersymmetric gauge theory

We discuss DGLAP and BFKL evolution equations in the N=4 supersymmetric gauge theory in the leading and next-to-leading approximations. Eigenvalues of the BFKL kernel in this model turn out to be analytic functions of the conformal spin. It allows us to find the residues of the anomalous dimensions of the twist-2 operators in the points j=1, 0, -1,... from the BFKL equation in an agreement with their direct calculation from the DGLAP equation. The holomorphic separability of the BFKL kernel and the integrability of the DGLAP dynamics in this model are also discussed. (orig.)Available from TIB Hannover: RA 2999(02-002) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

HECTOR 1.00. A program for the calculation of QED, QCD and electroweak corrections to ep and lpmN deep inelastic neutral and charged current scattering

A description of the Fortran program HECTOR for a variety of semi-analytical calculations of radiative QED, QCD, and electroweak corrections to the double-differential cross sections of NC and CC deep inelastic charged lepton proton (or lepton deuteron) scattering is presented. HECTOR originates from the substantially improved and extended earlier programs HELIOS and TERAD91. It is mainly intended for applications at HERA or LEP x LHC, but may be used also for #mu#N scattering in fixed target experiments. The QED corrections may be calculated in different sets of variables: leptonic, hadronic, mixed, Jaquet-Blondel, double angle etc. Besides the leading logarithmic approximation up to order O(#alpha#"2), exact O(#alpha#) corrections and inclusive soft photon exponentiation are taken into account. The photoproduction region is also covered. (orig.)44 refs.SIGLEAvailable from TIB Hannover: RA 2999(95-185) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekCommission of the European Communities (CEC), Brussels (Belgium)DEGerman

Complete O(#alpha#) QED corrections to the process ep#->#eX in mixed variables

The complete set of #OMICRON#(#alpha#) QED corrections with soft photon exponentiation to the process ep#->#eX in mixed variables (y=y_h, Q"2=Q_l"2) is calculated in the quark parton model. Compared to earlier attempts, we additionally determine the lepton-quark interference and the quarkonic corrections. The net results are compared to the approximation with only leptonic corrections, which amount to several percent (at large x or y: several dozens of percents). We find that the newly calculated corrections modify this by few percent or less and become negligible at small y. (orig.)7 refs.SIGLEAvailable from TIB Hannover: RA 2999(95-085) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The reaction NN #-># NN#gamma# in the 1 GeV region within an effective one-boson exchange model

Within an effective one-boson exchange parametrization of the T matrix of NN interactions we calculate cross sections for the reactions pp#->#pp#gamma# and pn#->#pn#gamma# for proton incidence energies in the order of 1 GeV. Besides bremsstrahlung processes we consider photons from #DELTA# decays and contributions from the #eta##->##gamma##gamma# process, where the #eta# is excited via the N_1_5_3_5 resonance. At beam energies above 700 MeV the #DELTA# decay channel dominates for large photon energies, while above the #eta# threshold the #eta# decay photons show up only in a narrow window. The low energy photons steam from pure bremsstrahlung processes. (orig.)22 refs.Available from TIB Hannover: RR 1847(95-118) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Bremsstrahlung in intermediate-energy nucleon reactions within an effective one-boson exchange model

Within a covariant effective one-boson exchange model for the T matrix of N N interactions we present detailed calculations of bremsstrahlung cross sections for proton - proton and proton - neutron reactions at beam energies in the 1 GeV region. Besides pure bremsstrahlung processes we consider photons from #DELTA# decays and contributions from the #eta##->##gamma##gamma# process. At beam energies above 700 MeV the #DELTA# decay channel dominates the spectra at large photon energies, where the interference between non-resonance processes and the #DELTA# decay channel becomes also important. Low energy photons stem from pure bremsstrahlung processes. The available experimental data at 730 MeV beam energy is well described. We extrapolate the model down to 280 MeV, where more detailed experimental data exist, and find agreement with angular distributions. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Asymmetry of the dielectron emission rate in an isospin-asymmetric pion medium

The dielectron emission by pion annihilation in an isospin-asymmetric pion gas at finite temperature is considered. Due to the difference between the longitudinal and transverse parts of the in-medium #rho# meson self-energy a specific asymmetry of the rate is caused for electron pairs with relative momenta perpendicular or parallel to the total pair momentum. This asymmetry may be considered as a sensitive signal of in-medium modifications of the #rho# properties. (orig.)12 refs.Available from TIB Hannover: RR 1847(95-113) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The quark condensate in relativistic nucleus-nucleus collisions

We compute the modification of the quark condensate left angle anti qq right angle in relativistic nucleus-nucleus collisions and estimate the 4-volume, where the quark condensate is small (left angle anti qq right angle / left angle anti qq right angle _0 #<=#0.1-0.3) using hadron phase-space distributions obtained with the quark-gluon string model. As a function of the beam energy the 4-volume rises sharply at a beam energy E_l_a_b/A #approx =#(2-5) GeV, remains roughly constant up to beam energies #approx =#20 GeV and rises at higher energies. At low energies the reduction of the condensate is mainly due to baryons, while at higher energies the rise of the 4-volume is due to the abundant mesons produced. Based on our results we expect that moderate beam energies on the order of 10 GeV per nucleon are favourable for studying the restoration of chiral symmetry in a baryon-rich environment in nucleus-nucleus collisions. (orig.)Available from TIB Hannover: RO 801(98-40) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman