46 research outputs found
Medium effects in the production and decay of vector mesons in pion-nucleus reactions
The -, - and -resonance production and their dileptonic
decay in reactions at 1.1 - 1.7 GeV/c are calculated within the
intranuclear cascade (INC) approach. The invariant mass distribution of the
dilepton pair for each resonance can be decomposed in two components which
correspond to their decay 'inside' the target nucleus and in the vacuum,
respectively. The first components are strongly distorted by the nuclear medium
due to resonance-nucleon scattering and a possible mass shift at finite baryon
density. These medium modifications are compared to background sources in the
dilepton spectrum from bremsstrahlung as well as the Dalitz decays of
and mesons produced in the reaction. Detailed predictions for
reactions at 1.3 and 1.7 GeV/c are made within several momentum bins
for the lepton pair.Comment: 29 pages, LaTeX, including 12 postscript figures, UGI-97-07, Nucl.
Phys. A., in pres
Probing the interactions of charmed mesons with nuclei in induced reactions
We study the perspectives of resonant and nonresonant charmed meson
production in reactions within the Multiple Scattering Monte
Carlo (MSMC) approach. We calculate the production of the resonances
and on various nuclei, their propagation
and decay to in the medium and
vacuum, respectively. The modifications of the open charm vector mesons in the
nuclear medium are found to be rather moderate or even small such that dilepton
spectroscopy will require an invariant mass resolution of a few MeV.
Furthermore, the elastic and inelastic interactions of the open charm mesons in
the medium are taken into account, which can be related to -, - or
-quark exchange with nucleons. It is found that by studying the
ratio for low momenta in the laboratory ( GeV/c) as a function of
target mass stringent constraints on the -quark exchange cross section
can be obtained. On the other hand, the ratios
as well as and at low momenta as a function
of will permit to fix independently the strength of the -quark exchange
reaction in scattering.Comment: 9 pages, LaTeX, including 9 postscript figures, submitted to Eur.
Phys. J.
Nuclear transparency in quasielastic A(e,e'p): intranuclear cascade versus eikonal approximation
The problem of nuclear propagation through the nuclear medium in quasielastic
A(e,e'p) reactions is discussed in the kinematic range 1<Q^2<7 (GeV/c)^2. The
coefficient of nuclear transparency is calculated for each Q^2 in the framework
of the intranuclear cascade model (INC) and of the eikonal approximation (EA).
The predictions of both models are in good agreement with each other and with
experimental data recently obtained at SLAC, BATES and TJNAF. The EA gives an
explanation of the Q^2 behaviour of the transparency coefficient as a kinematic
effect related to the superposition of contributions from each target shell.Comment: RevTeX, 23 pages, 11 figures separately, submitted to Phys. Rev.
Density dependence of resonance broadening and shadowing effects in nuclear photoabsorption
Medium effects as a function of the mass number are studied in the total
photonuclear cross section from the -resonance region up to the region
where shadowing effects are known to exist. A consistent picture is obtained by
simply assuming a density dependence of the different mechanisms of resonance
broadening and shadowing. The -mass shift is found to increase with
.Comment: 7 pages, LaTeX, 2 figures available from the author
Interactions of charmed mesons with nucleons in the reaction
We study the possibility to measure the elastic () scattering cross section in the
reaction and the elastic
scattering cross section in the reaction . Our
studies indicate that the elastic scattering cross sections can be determined
for momenta about 4-6 GeV/c and momenta 2 -- 5 GeV/c by
selecting events with GeV/c for 's and
0.5 GeV/c for -meson production.Comment: 7 pages, including 9 postscript figure
Studying the elastic and inelastic cross section with nucleons
We explore the possibility to measure the elastic and inelastic
cross section in and reactions. Our
studies indicate that the elastic scattering cross sections can be determined
for momenta above 1 GeV/c in reactions by gating on high
proton spectator momenta whereas the absorption cross section down
to low relative momenta is most effectively studied in
reactions at beam energies 2.0--2.7 GeVComment: 7 pages, svjour-style, including 9 ps-figure
Medium effects in the production and pi0 gamma decay of omega-mesons in pA collisions in the GeV region
The omega-resonance production and its pi0 gamma decay in p-A reactions close
to threshold is considered within the Intranuclear Cascade (INC) Model. The pi0
gamma invariant mass distribution shows two components which correspond to the
omega decay 'inside' and 'outside' the nucleus, respectively. The 'inside'
component is distorted by medium effects, which introduce a mass shift as well
as collisional broadening for the omega-meson and its decaying pion. The
relative contribution of the 'inside' component is analyzed in detail for
different kinematical conditions and nuclear targets. It is demonstrated that a
measurement of the correlation in azimuthal angle between the pi0 and gamma
momenta allows to separate events related to the 'inside' omega decay from
different sources of background when uncorrelated pi0's and gamma's are
produced.Comment: 24 pages, 11 figure