63 research outputs found
Zur mesonentheoretischen Beschreibung der Lambda-Nukleon-Wechselwirkung
Schon seit vielen Jahren ist man daran interessiert, eine theoretische Beschreibungvon Hyperkernen zu finden. Ideale Studienobjekte in diesem Gebietsind die leichten -Hyperkerne wie H, He, usw. Die ersten Arbeiten in diesem Bereich wurden durchgeführt von Herndong, Tang, Schmid (HTS65, HT67). Siebenutzten für ihre N-Streurechnungen ein einfaches spinabhängiges Zentralpotentialmit hard core, das sie aus der Analyse von s-Schalen-Hyperfragmentengewannen. Andere Autoren (BR70,73,DH70) übernahmen ein solches Zentralpotentialfür -Bindungsenergierechnungen oder benutzten andere Typen von effektivenWechselwirkungen, wie beispielsweise ein Potential vom Skyrme-Type (RAY76,81,B0U80).Das Problem bei diesen Rechnungen war und ist stets die "freie" N-Wechselwirkungals Ausgangspunkt für die Konstruktion einer effektiven N-Wechselwirkungim Medium. Diese mehr oder weniger phänomenologischen Ansätze, wie etwa da,sSkyrme-Potential, besitzen alle den Nachteil, nicht die ganze N-Wechselwirkungdarzustellen, sondern immer nur gewisse Partialwellen. So beschreibt z.B.das Zentralpotential von (HT65) nur die N-Wechselwirkung in s-Zuständen. [...
Weak strangeness production in nucleon-nucleon scattering
Until now the only way to study the strangeness changing baryon-baryon interaction has been through the decays of lambda hypernuclei. It would clearly be preferable to be able to study reactions such as pn→pΛ in free space. In order to provide some guidance concerning the feasibility of such a measurement, we investigate the energy dependence, parity violating asymmetry, and shape of the cross section for this reaction.J. Haidenbauer, K. Holinde, K. Kilian, T. Sefzick, A. W. Thoma
Comparison of the Near-Threshold Production of eta- and K-Mesons in Proton-Proton Collisions
The pp -> pp eta and pp -> pLambda K^+ reactions near threshold are dominated
by the first and second S_11 resonance respectively. It is shown that a
one-pion-exchange model exciting these isobars reproduces well the ratio of the
production cross sections. The consequences for this and other channels are
discussed.Comment: 10 pages, LaTeX2e, 1 eps-figur
The signal of in nucleon-antinucleon scattering
We study the production of at a nucleon-antinucleon scattering
experiment. Considering the PANDA experiment to be an ideal platform to explore
the production of the charmonium and charmonim-like states, we suggest the
forthcoming PANDA experiment to pay attention to the production of
.Comment: 6 pages, 15 figures. Published version in EPJ
The weak strangeness production reaction in a one-boson-exchange model
The weak production of Lambdas in nucleon-nucleon scattering is studied in a
meson-exchange framework. The weak transition operator for the reaction is identical to a previously developed weak
strangeness-changing transition potential that describes the
nonmesonic decay of hypernuclei. The initial and final state
interaction has been included by using realistic baryon-baryon forces that
describe the available elastic scattering data. The total and differential
cross sections as well as the parity-violating asymmetry are studied for the
reaction . These observables are found to be sensitive to the
choice of the strong interaction potential and the structure of the weak
transition potential.Comment: 25 pages, 8 postscript figures. Submitted to Phys. Rev.
Constraints on Parity-Even Time Reversal Violation in the Nucleon-Nucleon System and Its Connection to Charge Symmetry Breaking
Parity-even time reversal violation (TRV) in the nucleon-nucleon interaction
is reconsidered. The TRV -exchange interaction on which recent analyses
of measurements are based is necessarily also charge-symmetry breaking (CSB).
Limits on its strength relative to regular -exchange are
extracted from recent CSB experiments in neutron-proton scattering. The result
(95% CL) is considerably lower than limits
inferred from direct TRV tests in nuclear processes. Properties of
-exchange and limit imposed by the neutron EDM are briefly discussed.Comment: RevTex, 8 pages. Factor ten error in cited neutron EDM corrected,
discussion and two references adde
Testing the Meson Cloud Model in Inclusive Meson Production
We have applied the Meson Cloud Model to calculate inclusive momentum spectra
of pions and kaons produced in high energy proton-proton and proton-nucleus
collisions. For the first time these data are used to constrain the cloud
cut-off parameters. We show that it is possible to obtain a reasonable
description of data, especially the large () part of the
spectrum and at the same time describe (partially) the E866 data on and . We also discuss the relative strength of the
and vertices. We find out that the corresponding cut-off
parameters should be both soft and should not differ by more than 200 MeV from
each other. An additional source (other than the meson cloud) of sea antiquark
asymmetry, seems to be necessary to completely explain the data. A first
extension of the MCM to proton nucleus collisions is discussed.Comment: 14 pages, Latex, 6 ps figures. Submitted to Phys. Rev.
Short-range repulsion and isospin dependence in the KN system
The short-range properties of the KN interaction are studied within the
meson-exchange model of the Juelich group. Specifically, dynamical explanations
for the phenomenological short-range repulsion, required in this model for
achieving agreement with the empirical KN data, are explored. Evidence is found
that contributions from the exchange of a heavy scalar-isovector meson
(a_0(980)) as well as from genuine quark-gluon exchange processes are needed.
Taking both mechanisms into account a satisfactory description of the KN phase
shifts can be obtained without resorting to phenomenological pieces.Comment: 26 pages, 5 figure
Combined Description of Scattering and Annihilation With A Hadronic Model
A model for the nucleon-antinucleon interaction is presented which is based
on meson-baryon dynamics. The elastic part is the -parity transform of the
Bonn potential. Annihilation into two mesons is described in terms of
microscopic baryon-exchange processes including all possible combinations of
. The remaining
annihilation part is taken into account by a phenomenological energy- and state
independent optical potential of Gaussian form. The model enables a
simultaneous description of nucleon-antinucleon scattering and annihilation
phenomena with fair quality.Comment: revised version, REVTEX, 9 pages, 10 figures available from this URL
ftp://ikp113.ikp.kfa-juelich.de/pub/kph140/nucl-th.9411014.u
Non-perturbative structure of the polarized nucleon sea
We investigate the flavour and quark-antiquark structure of the polarized
nucleon by calculating the parton distribution functions of the nucleon sea
using the meson cloud model. We find that the SU(2) flavor symmetry in the
light antiquark sea and quark-antiquark symmetry in the strange quark sea are
broken, {\it i.e.} \Delta\ubar < \Delta \dbar and \Delta s < \Delta \sbar.
The polarization of the strange sea is found to be positive, which is in
contradiction to previous analyses. We predict a much larger quark-antiquark
asymmetry in the polarized strange quark sea than that in the unpolarized
strange quark sea. Our results for both polarized light quark sea and polarized
strange quark sea are consistent with the recent HERMES data.Comment: RevTex, 17 pages plus 8 PS figure
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