65 research outputs found
The Status of the Pion-Nucleon Coupling Constant
A review is given of the various determinations of the different piNN
coupling constants in analyses of the low-energy pp, np, pbarp, and pi-p
scattering data. The most accurate determinations are in the energy-dependent
partial-wave analyses of the NN data. The recommended value is f^2 = 0.075 . A
recent determination of f^2 by the Uppsala group from backward np cross
sections is shown to be model dependent and inaccurate, and therefore
completely uninteresting. We also argue that an accurate determination of f^2
using pp forward dispersion relations is not a realistic option.Comment: 19 pages, latex2e with a4wide.sty, more information is available at
http://NN-OnLine.sci.kun.nl . Invited talk at FBXV, Groningen, The
Netherlands, July 22-26, 1997. Invited talk at MENU97, Vancouver, B.C.,
Canada, July 28 - August 1, 199
Partial-Wave Analyses of all Proton-Proton and Neutron-Proton Data Below 500 MeV
In 1993 the Nijmegen group published the results of energy-dependent
partial-wave analyses (PWAs) of the nucleon-nucleon (NN) scattering data for
laboratory kinetic energies below Tlab=350 MeV (PWA93). In this talk some
general aspects, but also the newest developments on the Nijmegen NN PWAs are
reported. We have almost finished a new energy-dependent PWA and will discuss
some typical aspects of this new PWA; where it differs from PWA93, but also
what future developments might be, or should be.Comment: Presentation at the 19th European Conference on Few-Body Problems in
Physics, Groningen, The Netherlands, 23-27 August 2004. 4 pages REVTeX4, no
figure
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
On the nucleon self-energy in nuclear matter
We consider the nucleon self-energy in nuclear matter in the absence of Pauli
blocking. It is evaluated using the partial-wave analysis of scattering
data. Our results are compared with that of a realistic calculation to estimate
the effect of this blocking. It is also possible to use our results as a check
on the realistic calculations.Comment: 6 pages, 2 figure
The Goldberger-Treiman Discrepancy
The Golberger- Treiman discrepancy is related to the asymptotic behaviour of
the pionic form factor of the nucleon obtained from baryonic QCD sum rules. The
result is .015<=Delta_{GT}<=.022Comment: References updated and minor correction
The Nucleon-Mass Difference in Chiral Perturbation Theory and Nuclear Forces
A new method is developed for treating the effect of the neutron-proton mass
difference in isospin-violating nuclear forces. Previous treatments utilized an
awkward subtraction scheme to generate these forces. A field redefinition is
used to remove that mass difference from the Lagrangian (and hence from
asymptotic nucleon states) and replace its effect by effective interactions.
Previous calculations of static Class II charge-independence-breaking and Class
III charge-symmetry-breaking potentials are verified using the new scheme,
which is also used to calculate Class IV nuclear forces. Two-body forces of the
latter type are found to be identical to previously obtained results. A novel
three-body force is also found. Problems involving Galilean invariance with
Class IV one-pion-exchange forces are identified and resolved.Comment: 20 pages, 2 figures, latex - submitted to Physical Review
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
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