Charmonium Suppression with cc~ Dissociation by Strings

We study the production of cc~ pairs in nuclear reactions at SPS energies within the covariant transport approach HSD. The production of cc~ is treated perturbatively employing experimental cross sections while the interactions of cc~ pairs with baryons are included by conventional cascade-type two-body collisions. Adopting 6 mb for the cc~-baryon cross sections the data on J/\Psi suppression in p+A reactions are reproduced in line with calculations based on the Glauber model. Additionally the dissociation of the cc~ pairs by strings is included in a purely geometrical way. We find good agreement with experimental data from the NA38 and NA50 collaboration with an estimate for the string radius of ~0.2-0.3 fm.Comment: 9 pages (LaTeX), 5 PS figure

Beam spin asymmetry in deeply virtual π\pi production

An interpretation of the beam spin azimuthal asymmetries measured at JLAB in deep exclusive electroproduction of charged and neutral pions is presented. The model combines a Regge pole approach with the effect of nucleon resonances. The $s$- and $u$-channel contributions are described using a dual Bloom-Gilman connection between the exclusive form factors and inclusive deep inelastic structure functions. The results are in agreement with data provided the excitations of nucleon resonances are taken into account.Comment: 5 pages, 3 figures. Talk at the 19th International Spin Physics Symposium (SPIN2010), Sept.27-Oct.2, 2010, Juelich, German

Chromofields of Strings and Baryons

We calculate color electric fields of quark/antiquark ($\bar{q}q$) and 3 quark ($qqq$) systems within the chromodielectric model (CDM). We explicitly evaluate the string tension of flux tubes in the $\bar{q}q$--system and analyze their profile. To reproduce results of lattice calculations we use a bag pressure $B = (320 MeV)^4$ from which an effective strong coupling constant $\alpha_s \approx 0.3$ follows. With these parameters we get a $Y$ shaped configuration for large $qqq$--systems.Comment: Contributions to QNP 2002, Quarks and Nuclear Physics, Juelich, Germany 3 pages, 10 eps figure

Strangeness production in antiproton-nucleus annihilation

The results of the microscopic transport calculations of $\bar p$-nucleus interactions within a GiBUU model are presented. The dominating mechanism of hyperon production is the strangeness exchange processes $\bar K N \to Y \pi$ and $\bar K N \to \Xi K$. The calculated rapidity spectra of $\Xi$ hyperons are significantly shifted to forward rapidities with respect to the spectra of $S=-1$ hyperons. We argue that this shift should be a sensitive test for the possible exotic mechanisms of $\bar p$-nucleus annihilation. The production of the double $\Lambda$-hypernuclei by $\Xi^-$ interaction with a secondary target is calculated.Comment: Proceedings of the 12th Int. Workshop on Meson Production, Properties and Interaction (MESON-2012), Cracow, 31.05-05.06.201

Charged Current Neutrino Nucleus Interactions at Intermediate Energies

We have developed a model to describe the interactions of neutrinos with nucleons and nuclei, focusing on the region of the quasielastic and Delta(1232) peaks. We describe neutrino nucleon collisions with a fully relativistic formalism which incorporates state-of-the-art parametrizations of the form factors for both the nucleon and the N-Delta transition. The model has then been extended to finite nuclei, taking into account nuclear effects such as Fermi motion, Pauli blocking (both within the local density approximation), nuclear binding and final state interactions. The in-medium modification of the Delta resonance due to Pauli blocking and collisional broadening have also been included. Final state interactions are implemented by means of the Boltzmann-Uehling-Uhlenbeck (BUU) coupled-channel transport model. Results for charged current inclusive cross sections and exclusive channels as pion production and nucleon knockout are presented and discussed.Comment: 26 pages, 24 figures; v2: 2 figures and discussion added, version accepted for publication in Phys. Rev.