862 research outputs found
Light hypernuclei in four-body cluster models
Detailed structure calculations in Be, H,
Li, H and Li are performed
within the framework of the microscopic two-, three- and four-body cluster
models using the Gaussian Expansion Method.Comment: 14 pages, 19 figures. To be published in Phys. Rev.
Partial Wave Analyses of the pp data alone and of the np data alone
We present results of the Nijmegen partial-wave analyses of all NN scattering
data below Tlab = 500 MeV. We have been able to extract for the first time the
important np phase shifts for both I = 0 and I = 1 from the np scattering data
alone. This allows us to study the charge independence breaking between the pp
and np I = 1 phases. In our analyses we obtain for the pp data chi^2_{min}/Ndf
= 1.13 and for the np data chi^2_{min}/Ndf = 1.12.Comment: Report THEF-NYM 94.04, 4 pages LaTeX, one PostScript figure appended.
Contribution to the 14th Few-Body Conference, May 26 - 31, Williamsburg, V
Soft-core baryon-baryon potentials for the complete baryon octet
SU(3) symmetry relations on the recently constructed hyperon-nucleon
potentials are used to develop potential models for all possible baryon-baryon
interaction channels. The main focus is on the interaction channels with total
strangeness S=-2, -3, and -4, for which no experimental data exist yet. The
potential models for these channels are based on SU(3) extensions of potential
models for the S=0 and S=-1 sectors, which are fitted to experimental data.
Although the SU(3) symmetry is not taken to be exact, the S=0 and S=-1 sectors
still provide the necessary constraints to fix all free parameters. The
potentials for the S=-2, -3, and -4 sectors, therefore, do not contain any
additional free parameters, which makes them the first models of this kind.
Various properties of the potentials are illustrated by giving results for
scattering lengths, bound states, and total cross sections.Comment: 22 pages RevTex, 6 postscript figure
Soft-core hyperon-nucleon potentials
A new Nijmegen soft-core OBE potential model is presented for the low-energy
YN interactions. Besides the results for the fit to the scattering data, which
largely defines the model, we also present some applications to hypernuclear
systems using the G-matrix method. An important innovation with respect to the
original soft-core potential is the assignment of the cut-off masses for the
baryon-baryon-meson (BBM) vertices in accordance with broken SU(3), which
serves to connect the NN and the YN channels. As a novel feature, we allow for
medium strong breaking of the coupling constants, using the model with
a Gell-Mann--Okubo hypercharge breaking for the BBM coupling. We present six
hyperon-nucleon potentials which describe the available YN cross section data
equally well, but which exhibit some differences on a more detailed level. The
differences are constructed such that the models encompass a range of
scattering lengths in the and channels. For the
scalar-meson mixing angle we obtained values to 40 degrees, which
points to almost ideal mixing angles for the scalar states. The
G-matrix results indicate that the remarkably different spin-spin terms of the
six potentials appear specifically in the energy spectra of
hypernuclei.Comment: 37 pages, 4 figure
Role of the meson in photoproduction off the deuteron
Neutral kaon photoproduction off the nucleon and deuteron has been
reinvestigated by utilizing the new experimental data on both targets. An
isobar model for elementary operator and impulse approximation for the reaction
on the deuteron have been used. The available free parameters in the elementary
model have been extracted from both elementary and deuteron data. In contrast
to the elementary reaction, fitting the deuteron data requires an inclusion of
weighting factor. The result indicates that the angular distribution of the
elementary process does not show backward peaking behavior.Comment: 4 pages, 4 figures, prepared for the Fifth Asia-Pacific Conference on
Few-Body Problems in Physics 2011 (APFB2011), Seoul, Korea, August 22-26,
201
Soft two-meson-exchange nucleon-nucleon potentials. I. Planar and crossed-box diagrams
Pion-meson-exchange nucleon-nucleon potentials are derived for two nucleons
in the intermediate states. The mesons we include are (i) pseudoscalar mesons:
; (ii) vector mesons: ; (iii) scalar
mesons: ; and (iv) the
contribution from the Pomeron. Strong dynamical pair suppression is assumed,
and at the nucleon-nucleon-meson vertices Gaussian form factors are
incorporated into the relativistic two-body framework using a dispersion
representation for the pion- and meson-exchange amplitudes. The Fourier
transformations are performed using factorization techniques for the energy
denominators. The potentials are first calculated in the adiabatic
approximation to all planar and crossed three-dimensional momentum-space
-meson diagrams. Next, we calculate the corrections.Comment: 28 pages RevTeX, 8 postscript figures; revised version as to appear
in Phys. Rev.
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