2,255 research outputs found
Collective multipole expansions and the perturbation theory in the quantum three-body problem
The perturbation theory with respect to the potential energy of three
particles is considered. The first-order correction to the continuum wave
function of three free particles is derived. It is shown that the use of the
collective multipole expansion of the free three-body Green function over the
set of Wigner -functions can reduce the dimensionality of perturbative
matrix elements from twelve to six. The explicit expressions for the
coefficients of the collective multipole expansion of the free Green function
are derived. It is found that the -wave multipole coefficient depends only
upon three variables instead of six as higher multipoles do. The possible
applications of the developed theory to the three-body molecular break-up
processes are discussed.Comment: 20 pages, 2 figure
The role of the pion cloud in electroproduction of the (1232)
We calculate the ratios and of the multipole amplitudes for
electroproduction of the (1232) in the range of photon virtuality
~GeV in a chiral chromodielectric model and a linear
-model. We find that relatively large experimental values can be
explained in terms of the pion contribution alone; the contribution arising
from d-state quark admixture remains below 10\%. We describe the pion cloud as
a coherent state and use spin and isospin projection to obtain the physical
nucleon and the . The and amplitudes are reasonably
well reproduced in the -model; in the chromodielectric model, however,
they are a factor of two too small.Comment: 10 pages LaTeX2e, 3 LaTeX figures within the text; Requires
elsart.cls (included in the self-unpacking uuencoded gzipped file). (Accepted
for publication in Phys. Lett. B
Nucleon-Nucleon Correlations and Final State Interaction in Inclusive Quasi-Elastic Electron Scattering off Nuclei at x>1
Inclusive quasi-elastic electron scattering off nuclei is investigated at
high momentum transfer (Q^2>1 (GeV/c)^2) and x>1 adopting a consistent
treatment of nucleon-nucleon correlations in initial and final states. It is
shown that in case of light as well as complex nuclei the inclusive cross
section at 1.3<x<2 is dominated by the absorption of the virtual photon on a
pair of correlated nucleons and by their elastic rescattering in the continuum,
whereas at x>2 it is governed by the rescattering of the outgoing
off-mass-shell nucleon in the complex optical potential generated by the ground
state of the residual (A-1)-nucleon system.Comment: 06100 Perugia, Italy (b) Istituto Nazionale di Fisica Nucleare,
Sezione Sanita', Viale Regina Elena 299, I-00161 Roma, Italy 8 pages,
preprint INFN-ISS 94/1, January 1994 (to appear in Phys. Lett. B
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