14,839 research outputs found
Generalized Density Matrix Revisited: Microscopic Approach to Collective Dynamics in Soft Spherical Nuclei
The generalized density matrix (GDM) method is used to calculate
microscopically the parameters of the collective Hamiltonian. Higher order
anharmonicities are obtained consistently with the lowest order results, the
mean field [Hartree-Fock-Bogoliubov (HFB) equation] and the harmonic potential
[quasiparticle random phase approximation (QRPA)]. The method is applied to
soft spherical nuclei, where the anharmonicities are essential for restoring
the stability of the system, as the harmonic potential becomes small or
negative. The approach is tested in three models of increasing complexity: the
Lipkin model, model with factorizable forces, and the quadrupole plus pairing
model.Comment: submitted to Physical Review C on 08 May, 201
Hexadecapole Interaction and the Delta I=4 Staggering Effect in Rotational Bands
A role of the multipole interaction in the description of the =4
staggering phenomenon is investigated in a model consisting of a single-
shell filled by identical nucleons. Exact diagonalization of the
quadrupole-plus-hexadecapole Hamiltonian shows that the
hexadecapole-hexadecapole interaction can produce a =4 periodicity
in the yrast sequence.Comment: revised version with technical changes only, to be published in
Physica Scripta, latex, 4 pages, 3 PostScript figures available on request
from [email protected], preprint No. IFT/18/9
Could we learn more about HERA high anomaly from LEP200 and TEVATRON? R-parity violation scenario
The excess of high events at HERA reported in the early 1997 by H1 and
ZEUS collaborations has become the subject of extensive studies in the
framework of several models related to new physics. Here we concentrate on the
most promising, from our point of view, model describing HERA anomaly. We
update our previous analysis and take into account new HERA statistics of the
1997 year. HERA events are considered within the R-parity broken SUSY model for
a specific scenario with several non-zero couplings. R-parity broken SUSY with
several non-zero couplings could explain both high and observed at HERA. The consequence of such a particular scenario is the
excess of high di- or tri-jet events at HERA. The relation of this
scenario for LEP and TEVATRON colliders is considered. This study shows that if
a squark resonance does take place at HERA, supersymmetry with broken R-parity
can be revealed at either LEP200 or TEVATRON in the near future.Comment: 15 pages, LaTeX file with 9 eps figure
Multiple Scattering Theory for Slow Neutrons (from thermal to ultracold)
The general theory of neutron scattering is presented, valid for the whole
domain of slow neutrons from thermal to ultracold. Particular attention is
given to multiple scattering which is the dominant process for ultracold
neutrons (UCN). For thermal and cold neutrons, when the multiple scattering in
the target can be neglected, the cross section is reduced to the known value. A
new expression for inelastic scattering cross section for UCN is proposed.
Dynamical processes in the target are taken into account and their influence on
inelastic scattering of UCN is analyzed.Comment: 28 pages, latex, 2 Postscript figures, submitted to the European
Physical Journal
The action for the (propagating) torsion and the limits on the torsion parameters from present experimental data
Starting from the well established form of the Dirac action coupled to the
electromagnetic and torsion field we find that there is some additional softly
broken local symmetry associated with torsion. This symmetry fixes the form of
divergences of the effective action after the spinor fields are integrated out.
Then the requirement of renormalizability fixes the torsion field to be
equivalent to some massive pseudovector and its action is fixed with accuracy
to the values of coupling constant of torsion-spinor interaction, mass of the
torsion and higher derivative terms. Implementing this action into the abelian
sector of the Standard Model we establish the upper bounds on the torsion mass
and coupling. In our study we used results of present experimental limits on
four-fermion contact interaction (LEP, HERA, SLAC, SLD, CCFR) and TEVATRON
limits on the cross section of new gauge boson, which could be produced as a
resonance at high energy collisions.Comment: 12 pages, LaTeX, 5 figures include
Analysis of the vertices , and with light-cone QCD sum rules
In this article, we calculate the strong coupling constants of the ,
and in the framework of the light-cone QCD sum
rules approach. The strong coupling constants of the meson-baryon-baryon are
the fundamental parameters in the one-boson exchange model which describes the
baryon-baryon interactions successfully. The numerical values are in agreement
with the existing calculations in part. The electric and magnetic
ratios deviate from the prediction of the vector meson dominance theory, the
SU(3) symmetry breaking effects are very large.Comment: 19 pages, 6 figures, revised version, add more discussions(Correct
writing errors
Continuum Coupling and Pair Correlation in Weakly Bound Deformed Nuclei
We formulate a new Hartree-Fock-Bogoliubov method applicable to weakly bound
deformed nuclei using the coordinate-space Green's function technique. An
emphasis is put on treatment of quasiparticle states in the continuum, on which
we impose the correct boundary condition of the asymptotic out-going wave. We
illustrate this method with numerical examples.Comment: 5 pages, 4 figures, Proceedings of the Japanese French Symposium -
New paradigms in Nuclear Physics, Paris, 29th September - 2nd October, to be
published in Int. J. of Modern Physics
Light-cone sum rules for the transitions for real photons
We examine the radiative transition at the real photon
point using the framework of light-cone QCD sum rules. In particular,
the sum rules for the transition form factors and are
determined up to twist 4. The result for agrees with experiment within
10% accuracy. The agreement for is also reasonable. In addition, we
derive new light-cone sum rules for the magnetic moments of nucleons, with a
complete account of twist-4 corrections based on a recent reanalysis of photon
distribution amplitudes.Comment: 34 pages, 9 figures, revised version, published in Phys. Rev. D, one
misplaced reference correcte
-pair Production in the Littlest Higgs Model with T parity in next-to-leading order QCD at LHC
In the framework of the littlest Higgs model with parity, we study the
-pair production at the CERN Large Hadron Collider up to the QCD
next-to-leading order (NLO). The kinematic distributions of final decay
products and the theoretical dependence of the cross section on the
factorization/renormalization scale are analyzed. We adopt the PROSPINO scheme
in the QCD NLO calculations to avoid double counting and keep the convergence
of the perturbative QCD description. Our numerical results show that the QCD
NLO corrections significantly reduce the scale uncertainty, and enhance the
leading order integrated cross section with a -factor in the range of
() with the symmetry breaking scale varying from
() to () at the LHC.
We find that it is possible to select the signal events of the -pair
production from the
background with high ratio of signature over background by taking proper lower
limits on transverse momenta, invariant mass of the final charged leptons and
the missing transverse momentum.Comment: 34 pages, 14 figures, 4 table
Pairing properties of superheavy nuclei
Pairing properties of even-even superheavy N=184 isotones are studied within
the Skyrme-Hartree-Fock+BCS approach. In the particle-hole channel we take the
Skyrme energy density functional SLy4, while in the particle-particle channel
we employ the seniority pairing force and zero-range delta-interactions with
different forms of density dependence. We conclude that the calculated static
fission trajectories weakly depend on the specific form of the delta-pairing
interaction. We also investigate the impact of triaxiality on the inner fission
barrier and find a rather strong Z dependence of the effect.Comment: 9 pages, 5 figures, submitted to International Journal of Modern
Physics
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