41 research outputs found
Antikaon Production in Proton-Nucleus Reactions and the properties in nuclear matter
We calculate the momentum-dependent potentials for and mesons in
a dispersion approach at nuclear density using the information from
the vacuum and scattering amplitudes, however, leaving out the
resonance contributions for the in-medium analysis. Whereas the potential
is found to be repulsive ( + 30 MeV) and to show only a moderate
momentum dependence, the selfenergy at normal nuclear matter density
turns out to be - 200 MeV at zero momentum in line with kaon atomic
data, however, decreases rapidly in magnitude for higher momenta. The antikaon
production in p + A reactions is calculated within a coupled transport approach
and compared to the data at KEK including different assumptions for the
antikaon potentials. Furthermore, detailed predictions are made for and reactions at 2.5 GeV in order to determine the
momentum dependent antikaon potential experimentally.Comment: 27 pages, LaTeX, including 14 ps-figures, UGI-98-1
The Role of Lambda(1405) in Kaon-Proton Interactions
S-wave scattering into various channels near threshold are analyzed in
heavy-baryon chiral perturbation theory with introduced as an
independent field. This is the approach that predicted the critical density
for negatively charged kaon condensation. We show that
chiral perturbation expansion treating the as elementary is
consistent with {\it all} threshold data including a double-charge-exchange
process suppressed at leading order of chiral expansion in the absence of the
. We also discuss S-wave scattering phase shifts at low
energy.Comment: 12 pages, epsfig.sty, 1 figure (uuencoded
Vector Meson Mixing and Charge Symmetry Violation
We discuss the consistency of the traditional vector meson dominance (VMD)
model for photons coupling to matter, with the vanishing of vector meson-meson
and meson-photon mixing self-energies at q^2=0. This vanishing of vector mixing
has been demonstrated in the context of rho-omega mixing for a large class of
effective theories. As a further constraint on such models, we here apply them
to a study of photon-meson mixing and VMD. As an example we compare the
predicted momentum dependence of one such model with a momentum-dependent
version of VMD discussed by Sakurai in the 1960's. We find that it produces a
result which is consistent with the traditional VMD phenomenology. We conclude
that comparison with VMD phenomenology can provide a useful constraint on such
models.Comment: 7 pages, uses epsfig.sty. Publication details added to title pag
Kaon-Nucleon Scattering from Chiral Lagrangians
The s-wave scattering amplitude is computed up to one-loop order
corresponding to next-to-next-to-leading order (or NLO in short) with a
heavy-baryon effective chiral Lagrangian. Constraining the low-energy constants
by on-shell scattering lengths, we obtain contributions of each chiral order up
to NLO and find that the chiral corrections are ``natural" in the sense of
viable effective field theories. We have also calculated off-shell -wave
scattering amplitudes relevant to kaonic atoms and condensation in
``nuclear star" matter including the effect of . The
amplitude is found to be quite sensitive to the intermediate
contribution, while the amplitude varies smoothly with the C.M. energy.
The crossing-even one-loop corrections are found to play an important role in
determining the higher-order chiral corrections.Comment: 14 pages and 2 figures(LaTeX), SNUTP-93-81. (References are added in
the reference [21]
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
Electromagnetic isoscalar rho-pi-gamma exchange current and the anomalous action
Using modern data, we first refit constants needed to complete an anomalous
pi-rho-omega-a_1 Lagrangian obtained within the approach of hidden local
symmetries. Then we derive from this Lagrangian electromagnetic isoscalar
rho-pi-gamma and rho-a_1-gamma currents needed in calculations of the deuteron
electromagnetic form factors at large momentum transfers.Comment: 16 pages, 1 figure, Latex, feynman, submitted to Nucl. Phys.
X(1835) as the Lowest Mass Pseudoscalar Glueball and Proton Spin Problem
We consider the parity doublet structure observed in high hadronic
excitations within the instanton model for the QCD vacuum. In the conventional
approach this doubling phenomenon is treated as a manifestation of the partial
restoration of chiral or symmetry. We demonstrate that the suppression
of direct instanton contribution to the masses of excited hadrons leads to the
partial symmetry restoration in hadron spectrum. The origin of X(1835)
resonance observed by BES Collaboration is studied upon the doublet structure.
We argue also how X(1835) be interpreted as the lowest pseudoscalar glueball
state, and derive its coupling constant to proton. It turns out that this
coupling is large and negative. Demonstrated is how this large coupling affects
the gluonic contribution to the proton spin.Comment: 12 pages, LaTex, 1 eps-figure, expanded discussion on mechanism of
parity doubling in high hadronic excitations, version to appear in
Phys.Lett.
The theory and phenomenology of polarized deep inelastic scattering
Comprehensive review paper on the theory and phenomenology of polarized deep
inelastic scattering, to appear in Physics ReportsComment: 113 pages, latex, 40 figures not included (hard copies available via
mail upon request to [email protected]