Identical Bands in Superdeformed Nuclei: A Relativistic Description

Relativistic Mean Field Theory in the rotating frame is used to describe superdeformed nuclei. Nuclear currents and the resulting spatial components of the vector meson fields are fully taken into account. Identical bands in neighboring Rare Earth nuclei are investigated and excellent agreement with recent experimental data is observed.Comment: 11 pages (Latex) and 4 figures (available upon request) TUM-ITP-Ko93/

Soft-hard interplay and factorization for baryon production in the target fragmentation region in ep collisions

We discuss baryon production in the nucleon fragmentation region in deep inelastic scattering. The dependence of the nucleon spectra on Bjorken-$x$ is evaluated within the parton model and in QCD, and ways to look for the break-down of the DGLAP approximation via baryon production are suggested. We argue also that the leading neutron production in these small $x$ processes is rather insensitive to the pion parton densities of the nucleon.Comment: 13 pages, LaTeX, 2 Postscript figures; Final version to appear in Phys. Lett.

Hadronization of a Quark-Gluon Plasma in the Chromodielectric Model

We have carried out simulations of the hadronization of a hot, ideal but effectively massive quark-gluon gas into color neutral clusters in the framework of the semi-classical SU(3) chromodielectric model. We have studied the possible quark-gluon compositions of clusters as well as the final mass distribution and spectra, aiming to obtain an insight into relations between hadronic spectral properties and the confinement mechanism in this model.Comment: 34 pages, 37 figure

Microscopic Study of Superdeformed Rotational Bands in 151Tb

Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is demonstrated that far going similarities between the two approaches exist and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J(2), are shown to exist. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed -- they are most likely related to the yet not optimal parametrization of the nuclear interactions used.Comment: 32 RevTeX pages, 15 figures included, submitted to Physical Review

Diffractive Heavy Quarkonium Photo- and Electroproduction in QCD

Hard diffractive photo- and electroproduction of heavy vector mesons ($J/\psi$ and $\Upsilon$) is evaluated within the leading $\alpha_s\ln{Q^2 \over\Lambda_{QCD}^2}$ approximation of QCD. In difference from our earlier work on that subject, also the production of transversely polarized vector mesons is calculated. Special emphasis is placed on the role of the vector meson's $q\bar q$ light-cone wave function. In that context, conventional non-relativistic quarkonium models and a light-front QCD bound state calculation are critically examined and confronted with QCD expectations. Our numerical analysis finds a significant high momentum tail in the latter wave functions and a deviation from the expected asymptotic behavior of $\phi_V(z,b=0)\propto z(1-z)$. We then design an interpolation to match the quarkonium models at large inter-quark separations with QCD expectations at small distances. We use these results to compare our predictions for the forward differential cross section of $J/\psi$ photo- and electroproduction with recent experimental results from HERA. In addition, our earlier discussion of $\rho^o$ electroproduction is updated in light of recent experimental and theoretical enhancements.Comment: 44 pages, LaTeX, 14 figures included using epsf.tex; Final version to appear in Phys. Rev.

Hard diffractive electroproduction of vector mesons in QCD

Hard diffractive electroproduction of longitudinally polarized vector mesons is calculated within the leading $\alpha_s\ln{Q^2\over\Lambda_{QCD}^2}$ approximation of QCD using the leading order parton densities within the nucleon. Novel QCD features of the production of excited states and of the restoration of flavor symmetry are analyzed. At the onset of the asymptotic regime, our analysis finds an important role of quark Fermi motion within the diffractively produced vector mesons, and we suggest to use this effect to measure the high momentum tail of the wave function of the vector mesons. We deduce a kinematical boundary for the region of applicability of the decomposition of the hard amplitudes over powers of $Q^2$ and/or a limit on the increase of the cross sections of hard processes at small $x$, and briefly analyze its consequences. We also estimate the nuclear attenuation of the diffractive electroproduction of vector mesons and compare with estimates of the shadowing of the longitudinal structure function.Comment: 64 pages, REVTeX, 16 figures optionally included using epsfig.sty, Revisions in regards to Charmonium photo- and electroproduction, final version to appear in Phys. Rev.

Special Issue: Proceedings of the 21st International Workshop on Computer Algebra in Scientific Computing (CASC 2019)

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