Electroproduction of hadrons on nuclei at GeV energies

We investigate coherence length effects and hadron attenuation in lepton scattering off nuclei in the kinematic regime of the HERMES experiment. The elementary electron-nucleon interaction is described within the event generator PYTHIA while a full coupled-channel treatment of the final state interactions is included by means of a BUU transport model. The results of our calculations are in good agreement with the experimentally measured transparency ratio of incoherent rho0 electroproduction off Nitrogen and the multiplicity ratio R_M^h for charged hadrons, pions, kaons, protons and anti-protons in deep inelastic scattering off Nitrogen and Krypton targets.Comment: 17 pages, 4 figures. Proceedings of 2nd Int. Conf. on Nuclear and Particle Physics with CEBAF at Jefferson Lab, Dubrovnik, 26-31 May 2003, to be published in Fizika

Nuclear shadowing and in-medium properties of the rho^0

We explain the early onset of shadowing in nuclear photoabsorption within a multiple scattering approach and discuss its relation to in-medium modifications of the rho^0.Comment: 4 pages, 2 figures, to appear in the proceedings of the 9th International Conference on the Structure of Baryons, Newport News, VA, USA, 3-8 Mar 200

Hadron attenuation by (pre)hadronic FSI at HERMES

We investigate hadron production in deep inelastic lepton-nucleus scattering in the kinematic regime of the HERMES experiment. Our calculations are carried out in the framework of a BUU transport model which contains the Lund event generators PYTHIA and FRITIOF for the simulation of high-energy elementary interactions. For the first time we consistently use the complete four-dimensional information of the Lund string break up vertices as input for our transport theoretical studies of (pre)hadronic final state interactions. We compare our results with experimental HERMES data on charged hadron attenuation.Comment: 6 pages, 2 figures, Presented at First Workshop on Quark-Hadron Duality and the Transition to pQCD, Frascati, Italy, 6-8 June 200

Space-Time Picture of Fragmentation in PYTHIA/JETSET for HERMES and RHIC

We examine the space-time evolution of (pre-)hadron production within the Lund string fragmentation model. The complete four-dimensional information of the string breaking vertices and the meeting points of the prehadron constituents are extracted for each single event in Monte Carlo simulations using the Jetset-part of Pythia. We discuss the implication on the deep inelastic lepton scattering experiments at HERMES as well as on observables in ultra-relativistic heavy ion collisions at RHIC, using Pythia also for modeling the hard part of the interaction.Comment: 15 pages, 7 figures, final version as accepted by Phys Lett

Hadron attenuation at HERMES by (pre)hadronic FSI

We investigate hadron formation in high energy electroproduction off complex nuclei in the framework of a BUU transport model. Our approach combines a quantum mechanical treatment of the photon's initial state interactions with a semi-classical coupled channel simulation of the (pre)hadronic final-state interactions (FSI). This allows us to study the hadron attenuation observed at HERMES and to get information on the space-time picture of hadron formation separately for $\pi^{\pm}$, $\pi^0$, $K^\pm$, $p$ and $\bar{p}$.Comment: 3 pages, 1 figure, Contributions to 8th International Workshop on Meson Production, Properties and Interaction (Meson 2004), Krakow, Poland, June 6-8 200

Hadronization in nuclear DIS and ultra-relativistic HIC

We present a transport theoretical analysis of hadron attenuation in deep inelastic lepton scattering (DIS) off complex nuclei in the kinematic regime of the HERMES experiment. The HERMES data indicate the presence of strong prehadronic final state interactions shortly after the elementary lepton-nucleon interaction. The contribution of such (pre-)hadronic final state interactions to the observed jet quenching in ultra-relaticistic heavy ion collisions (HIC) at RHIC is estimated under the assumption that a similar space-time picture for hadronization also holds in a hot hadronic medium. Our results show that an additional mechanism for jet quenching must be at work for most central collisions.Comment: 3 pages, 2 figures, to appear in the proceedings of the Particles and Nuclei International Conference (PANIC 05), Santa Fe, NM, USA, 24-28 Oct 200

Microscopic calculation of the phonon dynamics of Sr2_{2}RuO4_{4} compared with La2_{2}CuO4_{4}

The phonon dynamics of the low-temperature superconductor Sr$_{2}$RuO$_{4}$ is calculated quantitatively in linear response theory and compared with the structurally isomorphic high-temperature superconductor La$_{2}$CuO$_{4}$. Our calculation corrects for a typical deficit of LDA-based calculations which always predict a too large electronic $k_{z}$-dispersion insufficient to describe the c-axis response in the real materials. With a more realistic computation of the electronic band structure the frequency and wavevector dependent irreducible polarization part of the density response function is determined and used for adiabatic and nonadiabatic phonon calculations. Our analysis for Sr$_{2}$RuO$_{4}$ reveals important differences from the lattice dynamics of $p$- and $n$-doped cuprates. Consistent with experimental evidence from inelastic neutron scattering the anomalous doping related softening of the strongly coupling high-frequency oxygen bond-stretching modes (OBSM) which is generic for the cuprate superconductors is largely suppressed or completely absent, respectively, depending on the actual value of the on-site Coulomb repulsion of the Ru4d orbitals. Also the presence of a characteristic $\Lambda_{1}$-mode with a very steep dispersion coupling strongly with the electrons is missing in Sr$_{2}$RuO$_{4}$. Moreover, we evaluate the possibility of a phonon-plasmon scenario for Sr$_{2}$RuO$_{4}$ which has been shown recently to be realistic for La$_{2}$CuO$_{4}$. In contrast to La$_{2}$CuO$_{4}$ in Sr$_{2}$RuO$_{4}$ the very low lying plasmons are overdamped along the c-axis.Comment: 30 pages, 16 figures, 4 tables, 33 reference