REINA() DE TRABALHO SOBRE FiSICA NUCLEAR NO BRASIL

1 0 Interacao nucleon-nucleon - XX RTFNB
statement, is achieved when the kernel of the Bethe-
Salpeter equation is integrated in the light-front energy
(k- = k° k 3 ) in each momentum loop of the iterated
equation. The first step corresponds to perform the
k- integration in the original Bethe-Salpeter equation.
The forward propagating intermediate virtual state iu
the light-front, time appears explicitly, which has at
most three-particles: the intermediate boson plus the
other two bosons. In order to generate all light-front
forward propagating intermediate states with any number
of particles, we iterate the Bethe-Salpeter equation
as many time as we need. Using this method, we construct
the kernel of the Bethe-Salpeter equation with
at most four particles in the intermediate state, which
are composed by two intermediate bosons plus the other
two and corresponds to the one time iterated B. S.
equation. The truncation of the intermediate propagation
in a state with a maximum number of parti
ties, breaks the covariance of the 13.-S. equation, Thus,
increasing the number of particles in the intermediate
states, the covariance of the Light-Front 13.-S. equation
should he approached. We made numerical calculations
allowing up to four particles intermediate states, in
order to study the effect of the high Fock state components
in the hound two-boson system.
Work supported by FA.PESP and CNPq.
Interacio nucleon-nucleon
01/09/97
DISINTEGRATION OF THE DEUTERON
BY LINEARLY-POLARIZED PHOTONS AT
LOW ENERGIES
V. P. Larafaciftw l , M. N. MARTINS, M. T. F. DA
CRUZ, J. D. T. ARRUDA-NETO
Institute de Fs'sica da Universidade de Edo Paulo - IFUSP
Rua do Matti°, Trauessa R.187; 05508-900 Scio Paulo, SP,
Brasil
S. A. PASCHUK 2
Centro Federal de Eduction° Tecnoldgica do Parallel -
CEFET Curitiba, PR, Brasil
Yu. A. KASATKIN, V. V. DENYAN, I. G. EVSEEV,
V. M. KHVASTUNOV
Kharkov Institute of Physics, Ukraine
V. B. SHOSTAK
Kiev Institute of Nuclear Physics, Ukraine
This work presents results of the deuteron photodisintegration
cross section and the E-asymmetry, measured
with linearly polarized photons on the near-threshold
energy region. The data are compared with calculations
performed in the framework of the Lorentz-, gaugeinvariant
(LGI) and diagrammatic approaches, and the
Partovi and Laget models. Minimum discrimination requirements
for experiments in the low-energy region are
analysed.
The experiment was carried out in the direct beam of
the Kharkov 2-GeV linac. The experimental facility,
the main characteristics of the beam and some preliminary
results were described previously. In this work
only those aspects relevant to this particular deuteron
experiment will be presented.
The E-asymnietry data are well described in the framework
of the diagrammatic approach for meson exchange
currents (MEC) with final state interaction (FSI). An
analogous calculation in the lGI approach slightly overestimates
the data.
The data for d 774-(E.,,) are in good agreement with the
calculation in the LGI approach using the Paris deuteron
wave function (PDWF). The calculated L Pic, (6'7) is
not sensitive to FSI effects.
The data of li (E.7 ) for Bp = 90° are consistent with
the data obtained with non-polarized photons cg(E 7 )
, for Op = 0°. Both sets of data agree well with calculations
in the diagrammatic approach using the Bonn
model and MEC, with and without FSI. These two calculations
are indistinguishable in the energy region of
the measurements.
lOn leave from Kharkov Institute of Physics and Technology,
Ukraine.
TWO PION EXCHANGE NN POTENTIAL
AND N — a. SC ATTERING
L. A. BARREIRO, C. L. LIMA, M. R. ROBILOTTA
f/SP
It has been pointed out [1] that the intermediate corn
ponent of the NN interaction has an outer part, due
to the exchange of two pions, which is directly related
to off-shell w N scattering and hence strongly influenced
by chiral symmetry. In this work we discuss the possibility
of obtaining information on the intermediate part
of NN potential from the study of N scattering.
The a particle has no spin and isospin and hence cannot
couple to a single pion. Therefore, it is a rather suitable
system for the study of the intermediate part of
the nuclear interaction. When low energy neutrons and
protons (if we forget the Coulomb barrier) are considered
the angular momentum may be used to selcct the
various regions of the potential.
A relationship between the tail of the two-pion content
of the nucleon-nucleon potential and neutron-alpha
scattering observables was sought, We calculate the
energy dependence of the phase shift for S, P, D and F
waves for the Argone, Bonn, Nijmegen, Paris and SSC
potentials. A comparison bettwen these potentials exi
ting in the literature is under way. The result of this
comparison will allow to decide with potentials have the
correct two pion exchange contribution at. intermediate