13,742 research outputs found
Binding of eta_c meson with light nucleus
Binding energy of eta_c with ^4 He has been calculated on the basis of Yukawa
type potential. Final Rank Approximation (FRA) has been used for microscopical
treatment of the initial 5-body problem. The results are compared with the
results of the folding model and variational calculations.Comment: 5 pages, 1 figur
Perturbation of a lattice spectral band by a nearby resonance
A soluble model of weakly coupled "molecular" and "nuclear" Hamiltonians is
studied in order to exhibit explicitly the mechanism leading to the enhancement
of fusion probability in case of a narrow near-threshold nuclear resonance. We,
further, consider molecular cells of this type being arranged in lattice
structures. It is shown that if the real part of the narrow nuclear resonance
lies within the molecular band generated by the intercellular interaction, an
enhancement, proportional to the inverse width of the nuclear resonance, is to
be expected.Comment: RevTeX, 2 figures within the file. In May 2000 the title changed and
some minor corrections have been don
Decoherence Dynamics in Low-Dimensional Cold Atom Interferometers
We report on a study of the dynamics of decoherence of a matter-wave
interferometer, consisting of a pair of low-dimensional cold atom condensates
at finite temperature. We identify two distinct regimes in the time dependence
of the coherence factor of the interferometer: quantum and classical. Explicit
analytical results are obtained in both regimes. In particular, in the
two-dimensional (2D) case in the classical (long time) regime, we find that the
dynamics of decoherence is universal, exhibiting a power-law decay with an
exponent, proportional to the ratio of the temperature to the
Kosterlitz-Thouless temperature of a single 2D condensate. In the
one-dimensional (1D) case in the classical regime we find a universal
nonanalytic time dependence of decoherence, which is a consequence of the
nonhydrodynamic nature of damping in 1D liquids.Comment: 4 pages, published versio
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
Electroweak supersymmetric effects on high energy unpolarized and polarized single top production at LHC
We consider various processes of single top production at LHC in the
theoretical framework of the MSSM and examine the role of the supersymmetric
electroweak one-loop corrections in a special moderately light SUSY scenario,
in an initial parton-pair c.m. high energy range where a logarithmic asymptotic
expansion of Sudakov type can be used. We show that the electroweak virtual
effects are systematically large, definitely beyond the relative ten percent
size, particularly for a final pair where a special enhancement is
present. We show then in a qualitative way the kind of precision tests of the
model that would be obtainable from accurate measurements of the energy
distributions of the various cross sections and of the top polarization
asymmetries.Comment: 30 pages, 9 figure
Nuclear Schiff moment in nuclei with soft octupole and quadrupole vibrations
Nuclear forces violating parity and time reversal invariance (-odd) produce -odd nuclear moments, for example, the
nuclear Schiff moment. In turn, this moment can induce the electric dipole
moment in the atom. The nuclear Schiff moment is predicted to be enhanced in
nuclei with static quadrupole and octupole deformation. The analogous
suggestion of the enhanced contribution to the Schiff moment from the soft
collective quadrupole and octupole vibrations in spherical nuclei is tested in
this article in the framework of the quasiparticle random phase approximation
with separable quadrupole and octupole forces applied to the odd Ra
and Rn isotopes. We confirm the existence of the enhancement effect
due to the soft modes. However, in the standard approximation the enhancement
is strongly reduced by a small weight of the corresponding "particle + phonon"
component in a complicated wave function of a soft nucleus. The perspectives of
a better description of the structure of heavy soft nuclei are discussed.Comment: 27 pages, 3 figures, minor corrections in references adde
Three Jet Events and New Strong Couplings at LEP and NLC
We study the effects of new dimension--6 operators, resulting from a general
invariant effective Lagrangian, on
three jet production at LEP and at the Next Linear Collider. Contributions to
the total event rate and to some event shape variables are analysed in order to
establish bounds on these operators.Comment: 5 pages, LaTeX, 1 Figur
Effects of Universal Extra Dimensions on Higgs signals at LHC
A major focus at the Large Hadron Collider (LHC) will be Higgs boson studies
and it would be an interesting prospect to simultaneously probe for physics
beyond the Standard Model (SM) in the Higgs signals. In this work we show as to
what extent, the effects of Universal Extra Dimension (UED) can be isolated at
the LHC through the Higgs signals. By doing a detailed study of the different
uncertainties involved in the measurement of the rates for the process pp --> h
--> gamma gamma we estimate the extent to which these uncertainties can mask
the effects of the contributions coming from UED.Comment: 13 pages, LateX, Title changed, text and figures modified. Version to
appear in IJMP
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