11,683 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
Reevaluation of Neutron Electric Dipole Moment with QCD Sum Rules
We study the neutron electric dipole moment in the presence of the
CP-violating operators up to the dimension five in terms of the QCD sum rules.
It is found that the OPE calculation is robust when exploiting a particular
interpolating field for neutron, while there exist some uncertainties on the
phenomenological side. By using input parameters obtained from the lattice
calculation, we derive a conservative limit for the contributions of the CP
violating operators. We also show the detail of the derivation of the sum
rules.Comment: 33 pages, 5 figure
(D* to D + gamma) and (B* to B + gamma) as derived from QCD Sum Rules
The method of QCD sum rules in the presence of the external electromagnetic
field is used to analyze radiative decays of charmed or bottomed
mesons such as and , with the
susceptibilities obtained previously from the study of baryon magnetic moments.
Our predictions on decays agree very well with the experimental
data. There are differences among the various theoretical predictions on
decays but the data are not yet available.Comment: 11 pages, Late
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
The supermultiplet of boundary conditions in supergravity
Boundary conditions in supergravity on a manifold with boundary relate the
bulk gravitino to the boundary supercurrent, and the normal derivative of the
bulk metric to the boundary energy-momentum tensor. In the 3D N=1 setting, we
show that these boundary conditions can be stated in a manifestly
supersymmetric form. We identify the Extrinsic Curvature Tensor Multiplet, and
show that boundary conditions set it equal to (a conjugate of) the boundary
supercurrent multiplet. Extension of our results to higher-dimensional models
(including the Randall-Sundrum and Horava-Witten scenarios) is discussed.Comment: 22 pages. JHEP format; references added; published versio
Semileptonic to Nucleon Transitions in Full QCD at Light Cone
The tree level semileptonic and
transitions are investigated using the light cone QCD sum rules approach in
full theory. The spin--1/2, baryon with or , is
considered by the most general form of its interpolating current. The time
ordering product of the initial and transition currents is expanded in terms of
the nucleon distribution amplitudes with different twists. Considering two sets
of independent input parameters entering to the nucleon wave functions, namely,
QCD sum rules and Lattice QCD parameters, the related form factors and their
heavy quark effective theory limits are calculated and compared with the
existing predictions of other approaches. It is shown that our results satisfy
the heavy quark symmetry relations for lattice input parameters and b case
exactly and the maximum violation is for charm case and QCD sum rules input
parameters. The obtained form factors are used to compute the transition rates
both in full theory and heavy quark effective theory. A comparison of the
results on decay rate of with those predicted by other
phenomenological methods or the same method in heavy quark effective theory
with different interpolating current and distribution amplitudes of the
is also presented.Comment: 18 Pages and 16 Table
CP violation in charged Higgs boson decays into tau and neutrino
We calculate the CP-violating rate asymmetry of H^\pm decays into tau and
neutrino at one loop in the MSSM with complex parameters. We find that the
asymmetry is typically of the order of 10^-3, depending mainly on the phases of
the trilinear coupling A_\tau and of the gaugino mass M_1.Comment: 9 pages, 3 figures, uses JHEP3.cl
Nuclear pairing reduction due to rotation and blocking
Nuclear pairing gaps of normally deformed and superdeformed nuclei are
investigated using the particle-number conserving (PNC) formalism for the
cranked shell model, in which the blocking effects are treated exactly. Both
rotational frequency -dependence and seniority (number of unpaired
particles) -dependence of the pairing gap are
investigated. For the ground-state bands of even-even nuclei, PNC calculations
show that in general decreases with increasing , but
the -dependence is much weaker than that calculated by the
number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle
bands (seniority ), the pairing gaps keep almost -independent.
As a function of the seniority , the bandhead pairing gaps
decrease slowly with increasing . Even for
the highest seniority bands identified so far,
remains greater than 70% of
.Comment: 15 pages, 5 figure
Pair production of charged Higgs scalars from electroweak gauge boson fusion
We compute the contribution to charged Higgs boson pair production at the
Large Hadron Collider (LHC) due to the scattering of two electroweak (EW) gauge
bosons, these being in turn generated via bremsstrahlung off incoming quarks: q
q --> q q V^*V^* --> q q H^+H^- (V=gamma,Z,W^{+/-}). We verify that the
production cross section of this mode is tan beta independent and show that it
is smaller than that of H^+H^- production via q q-initiated processes but
generally larger than that of the loop-induced channel gg --> H^+H^-. Pair
production of charged Higgs bosons is crucial in order to test EW symmetry
breaking scenarios beyond the Standard Model (SM). We show that the detection
of these kind of processes at the standard LHC is however problematic, because
of their poor production rates and the large backgrounds.Comment: 22 pages, latex, 8 figures (largely revised version to appear in JPG
Four-quark spectroscopy within the hyperspherical formalism
We present a generalization of the hyperspherical harmonic formalism to study
systems made of quarks and antiquarks of the same flavor. This generalization
is based on the symmetrization of the body wave function with respect to
the symmetric group using the Barnea and Novoselsky algorithm. The formalism is
applied to study four-quark systems by means of a constituent quark model
successful in the description of the two- and three-quark systems. The results
are compared to those obtained by means of variational approaches. Our analysis
shows that four-quark systems with exotic and non-exotic
quantum numbers may be bound independently of the mass of the quark.
and states become attractive only for larger mass of the quarks.Comment: 20 pages, 3 figure
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