4,592 research outputs found
Coulomb corrections to superallowed beta decay in nuclei
Corrections to the superallowed beta decay matrix elements are evaluated in
perturbation theory using the notion of the isovector monopole resonance. The
calculation avoids the separation into different contributions and thus
presents a consistent, systematic and more transparent approach. Explicit
expressions for the Coulomb correction as a function of mass number A, are
given.Comment: 10 page
Renormalization of the one-body off-diagonal Coulomb field in nuclei
Isospin violation effects in nuclei are investigated within a microscopic
approach which takes into account the influence of the residual strong
interaction on the Coulomb interaction. The renormalization of the off-diagonal
Coulomb field acting within a nucleus, by the residual strong interaction is
calculated analytically in a simplified RPA. From the expression for the
suppression coefficient of the isospin violating part of the Coulomb field, the
isospin violating spreading widths of isobaric analog states are derived. The
resulting reduction of the width is in agreement with the data on the isospin
symmetry restoration and with some earlier evaluations of the isospin violating
spreading widths.Comment: 11 pages, Late
"Super-radiance" and the width of exotic baryons
It is suggested that the narrow width of the recently observed resonance
with strangeness could be a result of the
super-radiance mechanism of the redistribution of the widths of overlapping
resonances due to their coupling through common decay channels.Comment: This is an update of the original version submitted on October 08,
2003; it includes consideration of an additional model and one new figur
Studies of highly-boosted top quarks near the TeV scale using jet masses at the LHC
Studies of highly-boosted top quarks produced inclusively in pp collisions at
14 TeV are discussed. The hadronic decays of boosted top quarks was studied in
a data-driven approach by analysing shapes of jet-mass distributions. Using
Monte Carlo models after a fast detector simulation, it is shown that inclusive
production of boosted top quarks can be observed if it has a cross section at
least twice larger than the prediction from the approximate
next-to-next-to-leading-order (aNNLO) calculation for the ttbar process. The
ttbar process with the nominal aNNLO strength can be measured using the masses
of jets after a b-tagging.Comment: 11 pages, 5 figure
The Effects of Deformation on Isovector Electromagnetic and Weak Transition Strengths
The summed strength for transitions from the ground state of via the
operators and
are calculated using the rotational
model. If we choose the z component of the isospin operator , the above
operators are relevant to electromagnetic transitions; if we choose
they are relevant to weak transitions such as neutrino capture. In going from
the spherical limit to the asymptotic (oblate) limit the strength for the
operator decreases steadily to zero; the strength for the operator
(scissors mode) increases by a factor of three. For the last
three operators - isovector dipole, spin dipole and orbital dipole (including
the twist mode) it is shown that the summed strength is independant of
deformation. The main difference in the behavior is that for the first two
operators we have in-shell transitions whereas for the last three operators the
transitions are out of shell.Comment: 14 pages, late
Widths of Isobaric Analog Resonances: a microscopic approach
A self-consistent particle-phonon coupling model is used to investigate the
properties of the isobaric analog resonance in Bi. It is shown that
quantitative agreement with experimental data for the energy and the width can
be obtained if the effects of isospin-breaking nuclear forces are included, in
addition to the Coulomb force effects. A connection between microscopic model
predictions and doorway state approaches which make use of the isovector
monopole resonance, is established via a phenomenological ansatz for the
optical potential.Comment: 18 pages, 1 figure. To appear on Phys. Rev. C (tentatively scheduled
for June 1998
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