18,755 research outputs found
Nuclear structure calculations for two-neutrino double-beta decay
We study the two-neutrino double-beta decay in 76Ge, 116Cd, 128Te, 130Te, and
150Nd, as well as the two Gamow-Teller branches that connect the double-beta
decay partners with the states in the intermediate nuclei. We use a theoretical
microscopic approach based on a deformed selfconsistent mean field with Skyrme
interactions including pairing and spin-isospin residual forces, which are
treated in a proton-neutron quasiparticle random-phase approximation. We
compare our results for Gamow-Teller strength distributions with experimental
information obtained from charge-exchange reactions. We also compare our
results for the two-neutrino double-beta decay nuclear matrix elements with
those extracted from the measured half-lives. Both single-state and
low-lying-state dominance hypotheses are analyzed theoretically and
experimentally making use of recent data from charge-exchange reactions and
beta decay of the intermediate nuclei.Comment: 11 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1502.0588
Theoretical mean field and experimental occupation probabilities in the double beta decay system 76Ge to 76Se
Usual Woods-Saxon single particle levels with BCS pairing are not able to
reproduce the experimental occupation probabilities of the proton and neutron
levels 1p_{3/2}, 1p_{1/2}, 0f_{5/2}, 0g_{9/2} in the double-beta decay system
76Ge to 76Se. Shifting down the 0g_{9/2} level by hand can explain the data but
it is not satisfactory. Here it is shown that a selfconsistent Hartree-Fock+BCS
approach with experimental deformations for 76Ge and 76Se may decisively
improve the agreement with the recent data on occupation probabilities by
Schiffer et al. and Kay et al. Best agreement with available data on 76Ge and
76Se, as well as on neighbor isotopes, is obtained when the spin-orbit strength
for neutrons is allowed to be larger than that for protons. The two-neutrino
double-beta decay matrix element is also shown to agree with data.Comment: 10 pages, 6 figure
Semi-inclusive charged-current neutrino-nucleus reactions
The general, universal formalism for semi-inclusive charged-current
(anti)neutrino-nucleus reactions is given for studies of any hadronic system,
namely, either nuclei or the nucleon itself. The detailed developments are
presented with the former in mind and are further specialized to cases where
the final-state charged lepton and an ejected nucleon are presumed to be
detected. General kinematics for such processes are summarized and then
explicit expressions are developed for the leptonic and hadronic tensors
involved and for the corresponding responses according to the usual charge,
longitudinal and transverse projections, keeping finite the masses of all
particles involved. In the case of the hadronic responses, general symmetry
principles are invoked to determine which contributions can occur. Finally, the
general leptonic-hadronic tensor contraction is given as well as the cross
section for the process
Coincidence charged-current neutrino-induced deuteron disintegration
Deuteron disintegration by charged-current neutrino (CC) scattering
offers the possibility to determine the energy of the incident neutrino by
measuring in coincidence two of the three resulting particles: a charged lepton
(usually a muon) and two protons, where we show that this channel can be
isolated from all other, for instance, from those with a pion in the final
state. We discuss the kinematics of the process for several detection
scenarios, both in terms of kinematic variables that are natural from a
theoretical point of view and others that are better matched to experimental
situations. The deuteron structure is obtained from a relativistic model
(involving an approximation to the Bethe-Salpeter equation) as an extension of
a previous, well-tested model used in deuteron electrodisintegration. We
provide inclusive and coincidence (semi-inclusive) cross sections for a variety
of kinematic conditions, using the plane-wave impulse approximation,
introducing final-state hadronic exchange terms (plane-wave Born approximation)
and final-state hadronic interactions (distorted-wave Born approximation).Comment: 31 pages, 14 figure
Algebraic computation of some intersection D-modules
Let be a complex analytic manifold, a locally
quasi-homogeneous free divisor, an integrable logarithmic connection with
respect to and the local system of the horizontal sections of on
. In this paper we give an algebraic description in terms of of the
regular holonomic D-module whose de Rham complex is the intersection complex
associated with . As an application, we perform some effective computations
in the case of quasi-homogeneous plane curves.Comment: 18 page
Nuclear shape dependence of Gamow-Teller distributions in neutron-deficient Pb isotopes
We study Gamow-Teller strength distributions in the neutron-deficient even
isotopes (184-194)Pb in a search for signatures of deformation. The microscopic
formalism used is based on a deformed quasiparticle random phase approximation
(QRPA) approach, which involves a self-consistent quasiparticle deformed Skyrme
Hartree-Fock (HF) basis and residual spin-isospin forces in both the
particle-hole and particle-particle channels. By analyzing the sensitivity of
the Gamow-Teller strength distributions to the various ingredients in the
formalism, we conclude that the beta-decay of these isotopes could be a useful
tool to look for fingerprints of nuclear deformation.Comment: 20 pages, 11 figures. To be published in Physical Review
Millimetre continuum observations of comet C/2009 P1 (Garradd)
Little is known about the physical properties of the nuclei of Oort cloud
comets. Measuring the thermal emission of a nucleus is one of the few means for
deriving its size and constraining some of its thermal properties. We attempted
to measure the nucleus size of the Oort cloud comet C/2009 P1 (Garradd). We
used the Plateau de Bure Interferometer to measure the millimetric thermal
emission of this comet at 157 GHz (1.9 mm) and 266 GHz (1.1 mm). Whereas the
observations at 266 GHz were not usable due to bad atmospheric conditions, we
derived a 3-sigma upper limit on the comet continuum emission of 0.41 mJy at
157 GHz. Using a thermal model for a spherical nucleus with standard thermal
parameters, we found an upper limit of 5.6 km for the radius. The dust
contribution to our signal is estimated to be negligible. Given the water
production rates measured for this comet and our upper limit, we estimated that
Garradd was very active, with an active fraction of its nucleus larger than
50%.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 2
figure
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