16,365 research outputs found
Neutrinoless double-beta decay matrix elements in large shell-model spaces with the generator-coordinate method
We use the generator-coordinate method with realistic shell-model
interactions to closely approximate full shell-model calculations of the matrix
elements for the neutrinoless double-beta decay of Ca, Ge, and
Se. We work in one major shell for the first isotope, in the
space for the second and third, and finally in two major
shells for all three. Our coordinates include not only the usual axial
deformation parameter , but also the triaxiality angle and
neutron-proton pairing amplitudes. In the smaller model spaces our matrix
elements agree well with those of full shell-model diagonalization, suggesting
that our Hamiltonian-based GCM captures most of the important valence-space
correlations. In two major shells, where exact diagonalization is not currently
possible, our matrix elements are only slightly different from those in a
single shell.Comment: 8 pages, 7 figure
Self-consistent description of multipole strength: systematic calculations
We use the quasiparticle random phase approximation with a few Skyrme density
functionals to calculate strength functions in the Jpi = 0+, 1-, and 2+
channels for even Ca, Ni, and Sn isotopes, from the proton drip line to the
neutron drip line. We show where and how low-lying strength begins to appear as
N increases. We also exhibit partial energy-weighted sums of the transition
strength as functions of N for all nuclei calculated, and transition densities
for many of the interesting peaks. We find that low-energy strength increases
with N in all multipoles, but with distinctive features in each. The low-lying
0+ strength near the neutron at large N barely involves protons at all, with
the strength coming primarily from a single two-quasineutron configuration with
very large spatial extent. The low-lying 1- strength is different, with protons
contributing to the transition density in the nuclear interior together with
neutrons at large radii. The low-lying 2+ transition strength goes largely to
more localized states. The three Skyrme interactions we test produce similar
results, differing most significantly in their predictions for the location of
the neutron drip line, the boundaries of deformed regions, energies of and
transition strengths to the lowest 2+ states between closed shells, and
isovector energy-weighted sum rules.Comment: 43 pages, 48 figures, 1 tabl
Model-independent assessment of current direct searches for spin-dependent dark matter
I evaluate the current results of spin-dependent weakly interacting massive
particle (WIMP) searches within a model-independent framework, showing the most
restrictive limits to date derive from the combination of xenon and sodium
iodide experiments. The extension of this analysis to the case of positive
signal experiments is elaborated.Comment: 4 pages, 4 figures, revised and accepted for publication on Phys.
Rev. Let
d-Au and p-p collisions at RHIC and the multichain Monte Carlo Dpmjet-III
In this paper we compare systematically the two-component Dual Parton Model
(DPM) event generator Dpmjet-III to d-Au and p-p data from RHIC. In this
process we are able to improve the model. The need for fusion of chains and a
recalibration of the model to obtain collision scaling in h-A and d-A
collisions was found already in previous comparisons. Here, comparing to
transverse momentum distributions of identified charged hadrons we find also
the need to modify the transverse momentum distributions in the decay of
hadronic strings, the basic building blocks of the model on soft hadronic
collisions.Comment: 8 pages, 13 figures, Based on a contribution to a workshop "QCD at
Cosmic Energies, Erice, Italie, Aug.29 to Sept.5 200
Antibaryon to Baryon Production Ratios in Pb-Pb and p-p collision at LHC energies of the DPMJET-III Monte Carlo
A sizable component of stopped baryons is predicted for pp and P bP b
collisions at LHC. Based on an analysis of RHIC data within framework of our
multichain Monte Carlo DPMJET-III the LHC predictions are presented.Comment: Presented at "Heavy Ion Collisions at the LHC: last call for
predictions", Geneva Switzerland, May 14th-June 8t
RHIC data and the multichain Monte Carlo DPMJET-II
Using data from RHIC we are able to systematically improve the two-component
Dual Parton Model (DPM) event generator DPMJET-III. Introducing percolation
parametrized as fusion of chains the model describes multiplicities and
pseudorapidity distributions in nucleus-nucleus collisions at all centralities.
Guided by the d-Au data from RHIC we recalibrate the model to obtain collision
scaling in h-A and d-A collisions.Comment: 8 pages, Based on a poster submitted to the 17th International
Conference on Ultra Relativistic Nucleus Nucleus Collisions, Jan. 11-17,
Oakland,California US
- …