25 research outputs found
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
Correlated and exchange in the baryon-baryon interaction
A dynamical model for correlated two-pion and two-kaon exchange in the
baryon- baryon interaction is presented, both in the scalar-isoscalar
() and the vector-isovector () channel. The correlations between
the two pseudoscalar mesons are taken into account by means of amplitudes derived from a meson-exchange model, which is in line with the
empirical data. It is found that correlated exchange plays
an important role in the -channel for baryon-baryon states with non-
vanishing strangeness. The strength of correlated plus
exchange in the -channel decreases with the strangeness of the baryon-
baryon system becoming more negative. The results for correlated -
exchange in the vector-isovector channel deviate from what is expected in the
naive SU(3) picture for genuine -exchange. Shortcomings of a simplified
description in terms of sharp mass - and -exchange are pointed
out.Comment: 51 pages, Latex file, figures available from
[email protected]
A dynamical model for correlated two-pion-exchange in the pion-nucleon interaction
A microscopic model for the process is presented in the
meson exchange framework, which in the pseudophysical region agrees with
available quasiempirical information. The scalar () and vector ()
piece of correlated two--pion exchange in the pion--nucleon interaction is then
derived via dispersion integrals over the unitarity cut. Inherent ambiguities
in the method and implications for the description of pion--nucleon scattering
data are discussed.Comment: 20 pages, 11 postscript figure
Near-threshold production of -mesons in and NN collisions and -mixing
We consider near-threshold -meson production in and
collisions. An effective Lagrangian approach with one-pion exchange is applied
to analyze different contributions to the cross section for different isospin
channels. The Reggeon exchange mechanism is also evaluated for comparison. The
results from reactions are used to calculate the contribution of the
meson to the cross sections and invariant mass distributions
of the reactions and . It is found that
the experimental observation of mesons in the reaction is much more promising than the observation of mesons in
the reaction . Effects of isospin violation in the reactions
, , and , which are induced by -- mixing, are also analyzed.Comment: 43 pages, including 16 eps figures, to be bublished in Phys. Atom.
Nucl. (Yad. Fiz.) vol. 65, No. 11 (2002
Near threshold enhancement of the ppbar mass spectrum in J/Psi decay
We investigate the nature of the near-threshold enhancement in the ppbar
invariant mass spectrum of the reaction J/Psi -> gamma ppbar reported recently
by the BES Collaboration. Using the Juelich NNbar model we show that the mass
dependence of the ppbar spectrum close to the threshold can be reproduced by
the S-wave ppbar final state interaction in the isospin I=1 state within the
Watson-Migdal approach. However, because of our poor knowledge of the NNbar
interaction near threshold and of the J/Psi -> gamma ppbar reaction mechanism
and in view of the controversal situation in the decay J/Psi -> pi0 ppbar,
where no obvious signs of a ppbar final state interaction are seen,
explanations other than final state interactions cannot be ruled out at the
present stage.Comment: 9 pages, 7 figure
Limits of the seismogenic zone in the epicentral region of the 26 December 2004 great Sumatra-Andaman earthquake: Results from seismic refraction and wide-angle reflection surveys and thermal modeling
The 26 December 2004 Sumatra earthquake (Mw = 9.1) initiated around 30 km
depth and ruptured 1300 km of the Indo-Australian Sunda plate boundary. During
the Sumatra OBS (ocean bottom seismometer) survey, a wide angle seismic profile
was acquired across the epicentral region. A seismic velocity model was
obtained from combined travel time tomography and forward modeling. Together
with reflection seismic data from the SeaCause II cruise, the deep structure of
the source region of the great earthquake is revealed. Four to five kilometers
of sediments overlie the oceanic crust at the trench, and the subducting slab
can be imaged down to a depth of 35 km. We find a crystalline backstop 120 km
from the trench axis, below the fore arc basin. A high velocity zone at the
lower landward limit of the raycovered domain, at 22 km depth, marks a shallow
continental Moho, 170 km from the trench. The deep structure obtained from the
seismic data was used to construct a thermal model of the fore arc in order to
predict the limits of the seismogenic zone along the plate boundary fault.
Assuming 100C-150C as its updip limit, the seismogenic zone is predicted to
begin 530 km from the trench. The downdip limit of the 2004 rupture as inferred
from aftershocks is within the 350C 450C temperature range, but this limit is
210-250 km from the trench axis and is much deeper than the fore arc Moho. The
deeper part of the rupture occurred along the contact between the mantle wedge
and the downgoing plate