256 research outputs found
Meson -scaling in heavy-ion collisions at SIS energies
We perform systematical studies on transverse-mass spectra of ,
, , , and mesons for C + C, Ni + Ni, Au + Au
collisions at SIS energies within the HSD transport approach. We find that the
-spectra sensitively reflect the in-medium properties of the mesons. The
'bare mass' scenario leads to a general scaling behaviour for the meson
-spectra when including a mass shift due to the associate strangeness
production threshold for kaons and antikaons whereas a 'dropping' mass scheme
violates this -scaling. The relative slope parameters, however, provide
valuable information about the average meson potentials in the nuclear medium.Comment: 15 pages, LaTeX, including 4 postscript figures, UGI-97-29, submitted
to Phys. Lett.
Neutral current neutrino-nucleus interactions at intermediate energies
We have extended our model for charged current neutrino-nucleus interactions
to neutral current reactions. For the elementary neutrino-nucleon interaction,
we take into account quasielastic scattering, Delta excitation and the
excitation of the resonances in the second resonance region. Our model for the
neutrino-nucleus collisions includes in-medium effects such as Fermi motion,
Pauli blocking, nuclear binding, and final-state interactions. They are
implemented by means of the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU)
coupled-channel transport model. This allows us to study exclusive channels,
namely pion production and nucleon knockout. We find that final-state
interactions modify considerably the distributions through rescattering,
charge-exchange and absorption. Side-feeding induced by charge-exchange
scattering is important in both cases. In the case of pions, there is a strong
absorption associated with the in-medium pionless decay modes of the Delta,
while nucleon knockout exhibits a considerable enhancement of low energy
nucleons due to rescattering. At neutrino energies above 1 GeV, we also obtain
that the contribution to nucleon knockout from Delta excitation is comparable
to that from quasielastic scattering.Comment: 16 pages, 10 figures; v2: version to be published in Phys. Rev. C,
comparison with results of Paschos et al. remove
Neutrino interactions with nucleons and nuclei at intermediate energies
We investigate neutrino-nucleus collisions at intermediate energies
incorporating quasielastic scattering and Delta(1232) excitation as elementary
processes, together with Fermi motion, Pauli blocking and mean-field potentials
in the nuclear medium. A full coupled-channel treatment of final state
interactions is achieved with a semiclassical BUU transport model. Results for
inclusive reactions and nucleon knockout are presented.Comment: Proceedings of PANIC'05, 3 pages, 3 figure
Color transparency in hadronic attenuation of rho0 mesons
Ongoing experiments at JLAB investigate the nuclear transparency in exclusive
rho0(770) electroproduction off nuclei. In this work we present transport model
predictions for the attenuation of rho0s in nuclei and for color transparency
(CT) effects as observable at CLAS with a 5 GeV electron beam energy. A full
event simulation presented here permits to study the impact of actual
experimental acceptance conditions and kinematical cuts. The exclusive
(e,e'rho0) cross section off nucleons is described by diffractive and color
string breaking mechanisms extended toward the onset of the deep inelastic
regime. Different hadronization and CT scenarios are compared. We show that a
detailed analysis of elementary cross section, nuclear effects and experimental
cuts is needed to reveal the early onset of rho0-CT at present JLAB energies.Comment: 10 pages, 11 figure
Low-energy pi pi photoproduction off nuclei
In the present paper we investigate pi0 pi0 and pi(+/-)pi0 photoproduction
off complex nuclei at incident beam energies of 400-460 MeV. Simulations of two
pion photoproduction on protons and nuclei are performed by means of a
semi-classical BUU transport model including a full coupled-channel treatment
of the final state interactions. Elastic scattering of the final state pions
with the nucleons in the surrounding nuclear medium is found to yield a
downward shift of the pi pi invariant mass distribution. We show that the
target mass dependence of the pi0 pi0 invariant mass spectrum as measured by
the TAPS collaboration can be explained without introducing medium effects
beyond absorption and quasi-elastic scattering of the final state particles. On
the other hand, we find considerable discrepancies with the data in the
pi(+/-)pi0 channel, which are not understood.Comment: 6 pages, 4 figure
Influence of the nucleon spectral function in photon and electron induced reactions on nuclei
We study the influence of the nucleon spectral function on eta photo- and
electroproduction on nuclei. Besides kinematical effects due to groundstate
correlations, also a modification of the S11(1535) decay width is taken into
account, which is caused by the possible decay into nucleons with mass smaller
than the pole mass in the medium. Hence, resonances with masses below the free
N eta threshold can contribute to eta production.Comment: 13 pages, 8 figure
The influence of the nuclear medium on inclusive electron and neutrino scattering off nuclei
We present a model for inclusive electron and neutrino scattering off nuclei
paying special attention to the influence of in-medium effects on the
quasi-elastic scattering and pion-production mechanisms. Our results for
electron scattering off Oxygen are compared to experimental data at beam
energies ranging from 0.7-1.5 GeV. The good description of electron scattering
serves as a benchmark for neutrino scattering.Comment: 6 pages, 3 figure
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