4,133 research outputs found
Distributions of the -matrix poles in Woods-Saxon and cut-off Woods-Saxon potentials
The positions of the -matrix poles are calculated in generalized
Woods-Saxon (GWS) potential and in cut-off generalized Woods-Saxon (CGWS)
potential. The solutions of the radial equations are calculated numerically for
the CGWS potential and analytically for GWS using the formalism of Gy. Bencze
\cite{[Be66]}. We calculate CGWS and GWS cases at small non-zero values of the
diffuseness in order to approach the square well potential and to be able to
separate effects of the radius parameter and the cut-off radius parameter. In
the case of the GWS potential the wave functions are reflected at the nuclear
radius therefore the distances of the resonant poles depend on the radius
parameter of the potential. In CGWS potential the wave function can be
reflected at larger distance where the potential is cut to zero and the
derivative of the potential does not exist. The positions of most of the
resonant poles do depend strongly on the cut-off radius of the potential, which
is an unphysical parameter. Only the positions of the few narrow resonances in
potentials with barrier are not sensitive to the cut-off distance. For the
broad resonances the effect of the cut-off can not be corrected by using a
suggested analytical form of the first order perturbation correction.Comment: Accepted by Nucl. Phys.
Search for supermassive magnetic monopoles using mica crystals
The survival of the Galactic magnetic field almost certainly sets an astrophysical upper bound of approx. 10 to the minus 15th power cm(-2) sr(-1) s(-1) on the flux of monopoles. To improve significantly upon this Parker limit with direct, real time searches would require a detector area of approx. 10,000 square meters and a collection time of years. Several such searches are being contemplated. A novel alternative scheme using large mica crystals capable of recording and storing tracks of slow monopoles over a time scale of approx. 10 to the 9th power years was proposed
Trajectories of the S-matrix poles in Salamon-Vertse potential
The trajectories of S-matrix poles are calculated in the finite-range
phenomenological potential introduced recently by P. Salamon and T. Vertse
(SV). The trajectories of the resonance poles in this SV potential are compared
to the corresponding trajectories in a cut-off Woods-Saxon (WS) potential for
l>0. The dependence on the cut-off radius is demonstrated. The starting points
of the trajectories turn out to be related to the average ranges of the two
terms in the SV potential
Calculating broad neutron resonances in a cut-off Woods-Saxon potential
In a cut-off Woods-Saxon (CWS) potential with realistic depth -matrix
poles being far from the imaginary wave number axis form a sequence where the
distances of the consecutive resonances are inversely proportional with the
cut-off radius value, which is an unphysical parameter. Other poles lying
closer to the imaginary wave number axis might have trajectories with irregular
shapes as the depth of the potential increases. Poles being close repel each
other, and their repulsion is responsible for the changes of the directions of
the corresponding trajectories. The repulsion might cause that certain
resonances become antibound and later resonances again when they collide on the
imaginary axis. The interaction is extremely sensitive to the cut-off radius
value, which is an apparent handicap of the CWS potential.Comment: 5 pages, 3 figure
A Penetration Depth Study on Li2Pd3B and Li2Pt3B
In this paper we present a penetration depth study on the newly discovered
superconductors LiPdB and LiPtB. Surprisingly, the
low-temperature penetration depth demonstrates distinct behavior in
these two isostructural compounds. In LiPdB, follows an
exponential decay and can be nicely fitted by a two-gap BCS superconducting
model with a small gap K and a large gap K.
However, linear temperature dependence of is observed in LiPtB
below 0.3, giving evidence of line nodes in the energy gap.Comment: 2 pages, submitted to LT2
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