2,466 research outputs found
Nucleon resonances in the constituent quark model with chiral symmetry
The mass spectra of nucleon resonances with spin 1/2, 3/2, and 5/2 are
systematically studied in the constituent quark model with meson-quark
coupling, which is inspired by the spontaneous breaking of chiral symmetry of
QCD.
The meson-quark coupling gives rise not only to the one-meson-exchange
potential between quarks but also to the self-energy of baryon resonances due
to the existence of meson-baryon decay channels.
The two contributions are consistently taken into account in the calculation.
The gross properties of the nucleon resonance spectra are reproduced fairly
well although the predicted mass of N(1440) is too high.Comment: 14 pages, 6 figures, Late
Energy Centroids of Spin States by Random Two-body Interactions
In this paper we study the behavior of energy centroids (denoted as
) of spin states in the presence of random two-body
interactions, for systems ranging from very simple systems (e.g. single-
shell for very small ) to very complicated systems (e.g., many- shells
with different parities and with isospin degree of freedom). Regularities of
's discussed in terms of the so-called geometric chaoticity (or
quasi-randomness of two-body coefficients of fractional parentage) in earlier
works are found to hold even for very simple systems in which one cannot assume
the geometric chaoticity. It is shown that the inclusion of isospin and parity
does not "break" the regularities of 's.Comment: four figures. to appear in Physical Review
Exchange Currents for Hypernuclear Magnetic Moments
The meson(K and ) exchange currents for the hypernuclear magnetic
moments are calculated using the effective Lagrangian method. The seagull
diagram, the mesonic diagram and the -excitation diagram are
considered. The -N exchange magnetic moments for the
, and are calculated
employing the harmonic oscillator shell model. It is found that the two-body
correction is about -9% of the single particle value for .
The exchange current, induced only in the -excitation diagram,
is found to give dominant contribution for the isovector magnetic moments of
hypernuclei with A=6.Comment: 11pp, LaTeX, 7 EPS figures, uses epsf.st
Educational and training opportunities as incentives for military service
The incentive value of the Navy Campus for Achievement (NCFA) for recruiting was evaluated using unobtrusive measures. Recruiter demand for a recruiting aid (brochure) solely featuring NCFA was compared against the demand for the most popular enlisted and officer aids. A Time magazine and TV Guide ad featuring NCFA was compared against other ads in Time and TV Guide over a 3-year period by the rate of return of coupons accompanying the ads. The material featuring NCFA compared as well or better (magazine ads) than the other material featuring general themes. The importance of educational and training opportunities, the seasonality and limitations of advertising in recruiting, and the methodology used in the evaluation are discussed and recommendations are made. (Author)supported by the Navy Personnel Research and Development Center, San Diego, Californiahttp://archive.org/details/educationaltrain00arimN68221 77 WR70088N
Ferroelectric polarization flop in a frustrated magnet MnWO induced by magnetic fields
The relationship between magnetic order and ferroelectric properties has been
investigated for MnWO with long-wavelength magnetic structure. Spontaneous
electric polarization is observed in an elliptical spiral spin phase. The
magnetic-field dependence of electric polarization indicates that the
noncollinear spin configuration plays a key role for the appearance of
ferroelectric phase. An electric polarization flop from the b direction to the
a direction has been observed when a magnetic field above 10T is applied along
the b axis. This result demonstrates that an electric polarization flop can be
induced by a magnetic field in a simple system without rare-earth f-moments.Comment: 9 pages, 4 figure
Electric Control of Spin Helicity in a Magnetic Ferroelectric
Magnetic ferroelectrics or multiferroics, which are currently extensively
explored, may provide a good arena to realize a novel magnetoelectric function.
Here we demonstrate the genuine electric control of the spiral magnetic
structure in one of such magnetic ferroelectrics, TbMnO3. A spin-polarized
neutron scattering experiment clearly shows that the spin helicity, clockwise
or counter-clockwise, is controlled by the direction of spontaneous
polarization and hence by the polarity of the small cooling electric field.Comment: 4 pages, 3 figure
Effect of the bound nucleon form factors on charged-current neutrino-nucleus scattering
We study the effect of bound nucleon form factors on charged-current
neutrino-nucleus scattering. The bound nucleon form factors of the vector and
axial-vector currents are calculated in the quark-meson coupling model. We
compute the inclusive C() cross sections using a
relativistic Fermi gas model with the calculated bound nucleon form factors.
The effect of the bound nucleon form factors for this reaction is a reduction
of 8% for the total cross section, relative to that calculated with the
free nucleon form factors.Comment: Latex, 11 pages, 3 figures, version to appear in Phys. Rev. C (Brief
Report
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