95 research outputs found
Pionic Degrees of Freedom in Atomic Nuclei and Quasielastic Knockout of Pions by High-Energy Electrons
The nonlinear model of pionic condensate in nuclei by G. Preparata can be
efficiently verified by investigation of the quasielastic knockout process of
pions out of nuclei by high energy electrons. First, a momentum distribution
(MD) of the collective pions has a bright maximum at q=0.3 Gev.Second the
excitation spectrum of a recoil nucleus is concentrated at low energies E
lesser than 1MeV. The results for the pion knockout from mesonic clouds of
individual nucleons are absolutely different. The latter results are presented
both for pion and rho-meson clouds localized on nucleons.Comment: 13 pages, 3 figure
Nucleon-nucleon wave function with short-range nodes and high-energy deuteron photodisintegration
We review a concept of the Moscow potential (MP) of the interaction. On
the basis of this concept we derive by quantum inversion optical partial
potentials from the modern partial-wave analysis (PWA) data and deuteron
properties. Point-form (PF) relativistic quantum mechanics (RQM) is applied to
the two-body deuteron photodisintegration. Calculations of the cross-section
angular distributions cover photon energies between 1.1 and 2.5 GeV. Good
agreement between our theory and recent experimental data confirms the concept
of deep attractive Moscow potential with forbidden - and -states.Comment: 31 pages, 9 figures. typos, extended formalism, review of the Moscow
potential model adde
Examination of the astrophysical S-factors of the radiative proton capture on 2H, 6Li, 7Li, 12C and 13C
Astrophysical S-factors of radiative capture reactions on light nuclei have
been calculated in a two-cluster potential model, taking into account the
separation of orbital states by the use of Young schemes. The local two-body
potentials describing the interaction of the clusters were determined by
fitting scattering data and properties of bound states. The many-body character
of the problem is approximatively accounted for by Pauli forbidden states. An
important feature of the approach is the consideration of the dependence of the
interaction potential between the clusters on the orbital Young schemes, which
determine the permutation symmetry of the nucleon system. Proton capture on 2H,
6Li, 7Li, 12C, and 13C was analyzed in this approach. Experimental data at low
energies were described reasonably well when the phase shifts for
cluster-cluster scattering, extracted from precise data, were used. This shows
that decreasing the experimental error on differential elastic scattering cross
sections of light nuclei at astrophysical energies is very important also to
allow a more accurate phase shift analysis. A future increase in precision will
allow more definite conclusions regarding the reaction mechanisms and
astrophysical conditions of thermonuclear reactions.Comment: 40p., 9 fig., 83 ref. arXiv admin note: substantial text overlap with
arXiv:1005.1794, arXiv:1112.1760, arXiv:1005.198
Microscopics of meson degrees of freedom in nucleons and mesons in nuclei - what can be seen in the process of quasielastic knockout of mesons by high-energy electrons
Developed earlier concept of quasielastic knock out of pions from nucleons by
high-energy electrons is propounded as a tool for checking microscopical model
( - fluctuation) for decay of N to different channels and
Preparata model of nucleus structure.Comment: 6 pages, 5 figures, Talk given at 16 Baldin Symposium in June 200
The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model
We study the short-range nucleon-nucleon interaction in a chiral constituent
quark model by diagonalizing a Hamiltonian comprising a linear confinement and
a Goldstone boson exchange interaction between quarks. The six-quark harmonic
oscillator basis contains up to two excitation quanta. We show that the highly
dominant configuration is due to its specific
flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a
strong effective repulsion at zero separation between nucleons in both
and channels. The symmetry structure of the highly dominant
configuration implies the existence of a node in the S-wave relative motion
wave function at short distances. The amplitude of the oscillation of the wave
function at short range will be however strongly suppressed. We discuss the
mechanism leading to the effective short-range repulsion within the chiral
constituent quark model as compared to that related with the one-gluon exchange
interaction.Comment: 31 pages, LaTe
Moscow-type NN-potentials and three-nucleon bound states
A detailed description of Moscow-type (M-type) potential models for the NN
interaction is given. The microscopic foundation of these models, which appear
as a consequence of the composite quark structure of nucleons, is discussed.
M-type models are shown to arise naturally in a coupled channel approach when
compound or bag-like six-quark states, strongly coupled to the NN channel, are
eliminated from the complete multiquark wave function. The role of the
deep-lying bound states that appear in these models is elucidated. By
introducing additional conditions of orthogonality to these compound six-quark
states, a continuous series of almost on-shell equivalent nonlocal interaction
models, characterized by a strong reduction or full absence of a local
repulsive core (M-type models), is generated. The predictions of these
interaction models for 3N systems are analyzed in detail. It is shown that
M-type models give, under certain conditions, a stronger binding of the 3N
system than the original phase-equivalent model with nodeless wave functions.
An analysis of the 3N system with the new versions of the Moscow NN potential
describing also the higher even partial waves is presented. Large deviations
from conventional NN force models are found for the momentum distribution in
the high momentum region. In particular, the Coulomb displacement energy for
nuclei ^3He - ^3H displays a promising agreement with experiment when the ^3H
binding energy is extrapolated to the experimental value.Comment: 23 pages Latex, 9 figures, to appear in Phys.Rev.
Role of the Nuclear and Electromagnetic Interactions in the Coherent Dissociation of the Relativistic Li Nucleus into the H + He Channel
The differential cross section in the transverse momentum and a total
cross section of mb for the coherent dissociation of a 3-A-GeV/
Li nucleus through the HHe channel have been measured on emulsion
nuclei. The observed dependence of the cross section is explained by the
predominant supposition of the nuclear diffraction patterns on light (C, N, O)
and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from
nuclear diffraction ( MeV/) and Coulomb MeV/)
dissociations are calculated to be 40.7 and 4 mb, respectively.Comment: ISSN 0021-3640, Pleiades Publishing, Ltd., 200
Multi-channel phase-equivalent transformation and supersymmetry
Phase-equivalent transformation of local interaction is generalized to the
multi-channel case. Generally, the transformation does not change the number of
the bound states in the system and their energies. However, with a special
choice of the parameters, the transformation removes one of the bound states
and is equivalent to the multi-channel supersymmetry transformation recently
suggested by Sparenberg and Baye. Using the transformation, it is also possible
to add a bound state to the discrete spectrum of the system at a given energy
if the angular momentum at least in one of the coupled channels .Comment: 9 pages, revtex; to be published in Phys. At. Nucl. (Oct. 2000
Astrophysical S-factor for the radiative capture reaction 13C(p,g)14N
The phase shift analysis, done on the basis of the known measurements of the
differential cross-sections of the p13C elastic scattering at the energy range
250-750 keV, shows that it is enough to take into account only 3S1 wave in the
considered energy region. The potential for the triplet 3S1 state in p13C
system at the resonance energy 0.55 MeV corresponding to quantum numbers JpT =
1-1 as well as the potential for the 3P1 bound state of 14N were constructed on
the basis of the obtained scattering phase shifts. The possibility to describe
the experimental data of the astrophysical S-factor of the p13C radiative
capture at the energies 0.03-0.8 MeV was considered within the potential
cluster model with the forbidden states. It was shown that we properly succeed
in explanation of the energy behavior of the astrophysical S-factor for the
p13C radiative capture at the resonance energy range 0.55 MeV (laboratory
system).Comment: 8 p., 2 fi
Nucleon-Nucleon Optical Model for Energies to 3 GeV
Several nucleon-nucleon potentials, Paris, Nijmegen, Argonne, and those
derived by quantum inversion, which describe the NN interaction for T-lab below
300$ MeV are extended in their range of application as NN optical models.
Extensions are made in r-space using complex separable potentials definable
with a wide range of form factor options including those of boundary condition
models. We use the latest phase shift analyses SP00 (FA00, WI00) of Arndt et
al. from 300 MeV to 3 GeV to determine these extensions. The imaginary parts of
the optical model interactions account for loss of flux into direct or resonant
production processes. The optical potential approach is of particular value as
it permits one to visualize fusion, and subsequent fission, of nucleons when
T-lab above 2 GeV. We do so by calculating the scattering wave functions to
specify the energy and radial dependences of flux losses and of probability
distributions. Furthermore, half-off the energy shell t-matrices are presented
as they are readily deduced with this approach. Such t-matrices are required
for studies of few- and many-body nuclear reactions.Comment: Latex, 40 postscript pages including 17 figure
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