611 research outputs found
High-precision covariant one-boson-exchange potentials for np scattering below 350 MeV
All realistic potential models for the two-nucleon interaction are to some
extent based on boson exchange. However, in order to achieve an essentially
perfect fit to the scattering data, characterized by a chi2/Ndata ~ 1, previous
potentials have abandoned a pure one boson-exchange mechanism (OBE). Using a
covariant theory, we have found a OBE potential that fits the 2006 world np
data below 350 MeV with a chi2/Ndata = 1.06 for 3788 data. Our potential has
fewer adjustable parameters than previous high-precision potentials, and also
reproduces the experimental triton binding energy without introducing
additional irreducible three-nucleon forces.Comment: 4 pages; revised version with augmented data sets; agrees with
published versio
Isospin symmetry breaking nucleon-nucleon potentials and nuclear structure
Modern nucleon-nucleon (NN) potentials, which accurately fit the
nucleon-nucleon scattering phase shifts, contain terms which break isospin
symmetry. The effects of these symmetry violating terms on the bulk properties
of nuclear matter are investigated. The predictions of the charge symmetry
breaking (CSB) terms are compared with the Nolen-Schiffer (NS) anomaly
regarding the energies of neighboring mirror nuclei. We find that, for a
quantitative explanation of the NS anomaly, it is crucial to include CSB in
partial waves with (besides ) as derived from a microscopic model
for CSB of the NN interaction.Comment: 14 pages, RevTex, 2 figure
Correlations derived from Modern Nucleon-Nucleon Potentials
Various modern nucleon-nucleon (NN) potentials yield a very accurate fit to
the nucleon-nucleon scattering phase shifts. The differences between these
interactions in describing properties of nuclear matter are investigated.
Various contributions to the total energy are evaluated employing the Hellmann
- Feynman theorem. Special attention is paid to the two-nucleon correlation
functions derived from these interactions. Differences in the predictions of
the various interactions can be traced back to the inclusion of non-local
terms.Comment: 7 pages, 4 figures include
Can the magnetic moment contribution explain the A_y puzzle?
We evaluate the full one-photon-exchange Born amplitude for scattering.
We include the contributions due to the magnetic moment of the proton or
neutron, and the magnetic moment and quadrupole moment of the deuteron. It is
found that the inclusion of the magnetic-moment interaction in the theoretical
description of the scattering observables cannot resolve the long-standing
puzzle.Comment: 7 pages, 2 Postscript figures; to appear in Phys.Rev.
Extraction of the coupling constant from NN scattering data
We reexamine Chew's method for extracting the coupling constant from
np differential cross section measurements. Values for this coupling are
extracted below 350 MeV, in the potential model region, and up to 1 GeV. The
analyses to 1~GeV have utilized 55 data sets. We compare these results to those
obtained via mapping techniques. We find that these two methods give
consistent results which are in agreement with previous Nijmegen
determinations.Comment: 12 pages of text plus 2 figures. Revtex file and postscript figures
available via anonymous FTP at ftp://clsaid.phys.vt.edu/pub/n
Comment on piNN Coupling from High Precision np Charge Exchange at 162 MeV
In this updated and expanded version of our delayed Comment we show that the
np backward cross section, as presented by the Uppsala group, is seriously
flawed (more than 25 sd.). The main reason is the incorrect normalization of
the data. We show also that their extrapolation method, used to determine the
charged piNN coupling constant, is a factor of about 10 less accurate than
claimed by Ericson et al. The large extrapolation error makes the determination
of the coupling constant by the Uppsala group totally uninteresting.Comment: 5 pages, latex2e with a4wide.sty. This is an updated and extended
version of the Comment published in Phys. Rev. Letters 81, 5253 (1998
Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev
We present two arguments indicating that the large value for the
mixing parameter at 50 MeV, which the Basel group extracted from their recent
measurement, may be incorrect. First, there are nucleon-nucleon (NN)
potentials which predict the at 50 MeV substantially below the
Basel value and reproduce the Basel data accurately. Second, the large
value for at 50 MeV proposed by the Basel group can only be
explained by a model for the NN interaction which is very unrealistic (no
-meson and essentially a point-like vertex) and overpredicts the
in the energy range where it is well determined (150--500 MeV) by
a factor of two.Comment: 6 pages text (LaTex) and 2 figures (paper, will be faxed upon
request), UI-NTH-930
Nonlocality of nucleon interaction and an anomalous off shell behavior of the two-nucleon amplitudes
The problem of the ultraviolet divergences that arise in describing the
nucleon dynamics at low energies is considered. By using the example of an
exactly solvable model it is shown that after renormalization the interaction
generating nucleon dynamics is nonlocal in time. Effects of such nonlocality on
low-energy nucleon dynamics are investigated. It is shown that nonlocality in
time of nucleon-nucleon interactions gives rise to an anomalous off-shell
behavior of the two-nucleon amplitudes that have significant effects on the
dynamics of many-nucleon systems.Comment: 9 pages, 4 figures, ReVTeX
LOCV calculation for Beta-stable matter at finite temperature
The method of lowest-order constrained variational, which predicts reasonably
the nuclear matter semi-empirical data is used to calculate the equation of
state of beta-stable matter at finite temperature. The Reid soft-core with and
without the N- interactions which fits the N-N scattering data as well
as the potential plus the three-nucleon interaction are considered in
the nuclear many-body Hamiltonian. The electron and muon are treated
relativistically in the total Hamiltonian at given temperature, to make the
fluid electrically neutral and stable against beta decay. The calculation is
performed for a wide range of baryon density and temperature which are of
interest in the astrophysics. The free energy, entropy, proton abundance, etc.
of nuclear beta-stable matter are calculated.
It is shown that by increasing the temperature, the maximum proton abundance
is pushed to the lower density while the maximum itself increases as we
increase the temperature. The proton fraction is not enough to see any
gas-liquid phase transition. Finally we get an overall agreement with other
many-body techniques, which are available only at zero temperature.Comment: LaTex, 20 page
Towards a Model-Independent Low Momentum Nucleon-Nucleon Interaction
We provide evidence for a high precision model-independent low momentum
nucleon-nucleon interaction. Performing a momentum-space renormalization group
decimation, we find that the effective interactions constructed from various
high precision nucleon-nucleon interaction models, such as the Paris, Bonn,
Nijmegen, Argonne, CD Bonn and Idaho potentials, are identical. This
model-independent low momentum interaction, called V_{low k}, reproduces the
same phase shifts and deuteron pole as the input potential models, without
ambiguous assumptions on the high momentum components, which are not
constrained by low energy data and lead to model-dependent results in many-body
applications. V_{low k} is energy-independent and does not necessitate the
calculation of the Brueckner G matrix.Comment: 12 pages, 5 figures, minor changes and additions, to appear in Phys.
Lett.
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