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

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

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

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

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

Hadron formation in electron induced reactions at HERMES energies

We investigate meson electroproduction off complex nuclei in the kinematic regime of the HERMES experiment using a semi-classical transport model which is based on the Boltzmann-Uehling-Uhlenbeck (BUU) equation. We discuss coherence length and color transparency effects in exclusive rho^0 production as well as hadron formation and attenuation of charged pions, kaons, protons and anti-protons in deep inelastic lepton scattering off nuclei.Comment: 5 pages, 2 figures, to be published in the Proceedings of the "10th International Conference on Hadron Spectroscopy", Aschaffenburg, Germany, Aug. 31 - Sep. 6, 200

In-Medium Properties of Hadrons - Observables II

In this review we discuss the observable consequences of in-medium changes of hadronic properties in reactions with elementary probes, and in particular photons, on nuclei. After an outline of the theoretical method used we focus on a discussion of actual observables in photonuclear reactions; we discuss in detail $2\pi$- and vector-meson production. We show that the $2\pi^0$ photoproduction data can be well described by final state interactions of the pions produced whereas the semi-charged $\pi^0\pi^\pm$ channel exhibits a major discrepancy with theory. For $\omega$ production on nuclei in the TAPS/CB@ELSA experiment we analyse the $\pi^0\gamma$ decay channel, and illustrate the strength of the method by simulating experimental acceptance problems. Completely free of final state interactions is dilepton production in the few GeV range. We show that the sensitivity of this decay channel to changes of hadronic properties in medium in photonuclear reactions on nuclei is as large as in ultrarelativistic heavy ion collisions and make predictions for the on-going G7 experiment at JLAB. Finally we discuss that hadron production in nuclei at 10 -- 20 GeV photon energies can give important information on the hadronization process, and in particular on the time-scales involved. We show here detailed calculations for the low-energy (12 GeV) run at HERMES and predictions for planned experiments at JLAB.Comment: Invited Talk by U. Mosel, Proceedings of the Int. School on Nuclear Physics, 26th Course, "Lepton scattering and the structure of hadrons and nuclei", Erice (Sicily), September 16th-24th, 2004, short piece of text adde