Search results for "acting"
showing 10 items of 338 documents
Single Particle Levels and ββ-Decay Matrix Elements in The Interacting Boson Model
2018
Recently a new method to calculate the occupancies of single particle levels in atomic nuclei was developed in the context of the microscopic interacting boson model, in which neutron and proton degrees of freedom are treated explicitly (IBM-2). The energies of the single particle levels constitute a very important input for the calculation of the occupancies in this method, and further they play important role in the calculation of double beta decay nuclear matrix elements. Here we discuss how the 0νββ, 0νhββ, and 2νββ-decay nuclear matrix elements (NMEs) are affected when the energies of single particle levels are changed. peerReviewed
The star formation activity in cosmic voids
2014
Using a sample of cosmic voids identified in the Sloan Digital Sky Survey Data Release 7, we study the star formation activity of void galaxies. The properties of galaxies living in voids are compared with those of galaxies living in the void shells and with a control sample, representing the general galaxy population. Void galaxies appear to form stars more efficiently than shell galaxies and the control sample. This result can not be interpreted as a consequence of the bias towards low masses in underdense regions, as void galaxy subsamples with the same mass distribution as the control sample also show statistically different specific star formation rates. This highlights the fact that g…
Investigation of nuclear collectivity in the neutron mid-shell nucleusPb186
2007
For the first time, non-yrast structures of the neutron mid-shell nucleus $^{186}\mathrm{Pb}$ have been identified in an in-beam \ensuremath{\gamma}-ray spectroscopy measurement using the recoil-decay tagging technique. The yrast band has been tentatively extended up to ${I}^{\ensuremath{\pi}}=20{}^{+},$ revealing a similar backbend to that observed in the Pt and Hg isotones. Three new bands and several other transitions have been observed. Calculations carried out in the framework of the interacting boson model together with mean-field studies using the generator coordinate method provide arguments for the association of one of the new bands with an oblate shape. The present data also show…
Exploring Mergers of Galaxy Clusters in a Cosmological Context
2010
We present results of an Eulerian Adaptive Mesh Refinement (AMR) hydrodynamical and N-body simulation in a ΛCDM cosmology. The simulation incorporates common cooling and heating processes, a phenomenological description of the star formation and supernovae feedback. A specific halo finder has been designed and applied in order to extract a sample of galaxy clusters directly obtained from the simulation without considering any resimulating scheme. We have studied the evolutionary history of the cluster halos, and classified them in three categories depending on the merger events they have undergone. We pay special attention to discuss the role of merger events as a source of feedback and reh…
On a differential system arising in the network control theory
2016
We investigate the three-dimensional dynamical system occurring in the network regulatory systems theory for specific choices of regulatory matrix { { 0, 1, 1 } { 1, 0, 1 } { 1, 1, 0 } } and sigmoidal regulatory function f(z) = 1 / (1 + e-μz), where z = ∑ Wij xj - θ. The description of attracting sets is provided. The attracting sets consist of respectively one, two or three critical points. This depends on whether the parameters (μ,θ) belong to a set Ω or to the complement of Ω or to the boundary of Ω, where Ω is fully defined set.
Shape evolution in116,118Ru: Triaxiality and transition between the O(6) and U(5) dynamical symmetries
2013
${}^{116}\mathrm{Ru}$ and ${}^{118}\mathrm{Ru}$ have been studied via $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin $J=6$ have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial $\ensuremath{\gamma}$-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neu…
Relativistic Coulomb excitation of Kr 88
2016
International audience; To investigate the systematics of mixed-symmetry states in N=52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum für Schwerionenforschung to determine E2 transition strengths to 2+ states of the radioactive nucleus $^{88}$Kr. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M1 transition to the fully symmetric 21+ state, extending the knowledge of the N=52 isotones below Z=40. A comparison with the proton-neutron interacting boson model and shell-model predictio…
Inelastic WIMP-nucleus scattering to the first excited state in125Te
2016
The direct detection of dark matter constituents, in particular the weakly interacting massive particles (WIMPs), is considered central to particle physics and cosmology. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Examples considered previously were the first excited states of $^{127}$I and $^{129}$Xe and $^{83}$Kr. Here we examine $^{125}$Te, which offers some advantages and is currently being considered as a target.In all these cases the extra signature of the gamma rays following the de-excitation of these states has definite advantages over the purely nuclear recoil and, in principle, such a signat…
First observation of excited states in the neutron deficient nuclei Pt and Pt
1998
Abstract Excited states have been observed for the first time in 168 Pt and 170 Pt using the α -decay recoil-tagging technique. The trend of decreasing deformation moving away from the N =104 mid-shell continues for 170 Pt but the structure of 168 Pt is significantly different. The low spin level energy systematics in 168 – 184 Pt are presented and discussed within the framework of the interacting boson model.
Theoretical direct WIMP detection rates for transitions to the first excited state inKr83
2015
The direct detection of dark matter constituents, in particular the weakly interacting massive particles (WIMPs), is central to particle physics and cosmology. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Examples considered previously were the first excited states of $^{127}\mathrm{I}$ and $^{129}\mathrm{Xe}$. We examine here $^{83}\mathrm{Kr}$, which offers some kinematical advantages and is a possible target. We estimate appreciable rates for the inelastic scattering mediated by the spin cross sections, with an inelastic event rate of $4.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ …