Search results for "Double beta"
showing 10 items of 320 documents
Half-Life Systematics across theN=126Shell Closure: Role of First-Forbidden Transitions in theβDecay of Heavy Neutron-Rich Nuclei
2014
This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic Pb208. The lifetimes of the 126-neutron shell isotone Pt204 and the neighboring Ir200-202, Pt203, Au204 are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first…
Observables sensitive to absolute neutrino masses. II
2008
In this followup to Phys. Rev. D 75, 053001 (2007) [arXiv:hep-ph/0608060] we report updated constraints on neutrino mass-mixing parameters, in light of recent neutrino oscillation data (KamLAND, SNO, and MINOS) and cosmological observations (WMAP 5-year and other data). We discuss their interplay with the final 0nu2beta decay results in 76-Ge claimed by part of the Heidelberg-Moscow Collaboration, using recent evaluations of the corresponding nuclear matrix elements, and their uncertainties. We also comment on the 0nu2beta limits in 130-Te recently set by Cuoricino, and on prospective limits or signals from the KATRIN experiment.
Gamow-Teller strengths in proton-rich exotic nuclei deduced in the combined analysis of mirror transitions
2005
Isospin symmetry is expected for the T-z=+/- 1 -> 0 isobaric analogous transitions in isobars with mass number A, where T-z is the z component of isospin T. Assuming this symmetry, strengths of analogous Gamow-Teller (GT) transitions within A=50 isobars were determined from a high energy-resolution T-z=+1 -> 0, Cr-50(He-3,t)Mn-50 study at 0 degrees in combination with the decay Q value and lifetime from the T-z=-1 -> 0, Fe-50 ->Mn-50 beta decay. This method can be applied to other pf-shell nuclei and can be used to study GT strengths of astrophysical interest.
Neutrinoless double beta decays of 106Cd revisited
2011
Abstract Neutrinoless double beta ( 0 ν 2 β ) decays of 106 Cd are studied for the transitions to the ground state, 0 gs + , and 0 + excited states in 106 Pd by using realistic many-body wave functions calculated in the framework of the quasiparticle random-phase approximation and its extensions. Effective, G-matrix-based nuclear forces are used in large single-particle model spaces. Both the β + β + and β + EC channels of the 0 ν 2 β decay are discussed and half-lives are computed. Particular attention is devoted to the study of the detectability of the resonant neutrinoless double electron capture ( R 0 ν ECEC ) process in 106 Cd. The calculations of the present article constitute the thu…
High-multiplicity neutron events registered by NEMESIS experiment
2021
Neutron-induced interactions contribute to the signal-mimicking background in deep-underground searches for exotic phenomena such as Dark Matter, neutrino-less double beta decay, proton decay, etc. Apart from radioactive decay, the primary source of neutrons underground are high-energy muons from cosmic showers. While the maximum number of fission neutrons is around six and energies around one MeV, muon-induced interactions may generate hundreds of neutrons, also with high energies. Furthermore, these processes are not yet reproduced in numerical simulations with sufficient reliability. The main goal of the NEMESIS experiment is to improve our knowledge and understanding of cosmic muon-indu…
Ordinary muon capture studies for the matrix elements in ββ decay
2018
Precise measurement of $\gamma$-rays following ordinary (non-radiative) capture of negative muons by natural Se, Kr, Cd and Sm, as well as isotopically enriched $^{48}$Ti, $^{76}$Se, $^{82}$Kr, $^{106}$Cd and $^{150}$Sm targets was performed by means of HPGe detectors. Energy and time distributions were investigated and total life time of negative muon in different isotopes was deduced. Detailed analysis of $\gamma$-lines intensity allows to extract relative yield of several daughter nuclei and partial rates of ($\mu$,$\nu$) capture to numerous excited levels of the $^{48}$Sc, $^{76}$As, $^{82}$Br, $^{106}$Ag and $^{150}$Tc isotopes which are considered to be virtual states of an intermedia…
Electron-capture branch ofTc100and tests of nuclear wave functions for double-βdecays
2008
We present a measurement of the electron-capture branch of $^{100}\mathrm{Tc}$. Our value, $B(\mathrm{EC})=(2.6\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, implies that the $^{100}\mathrm{Mo}$ neutrino absorption cross section to the ground state of $^{100}\mathrm{Tc}$ is roughly 50% larger than previously thought. Disagreement between the experimental value and QRPA calculations relevant to double-$\ensuremath{\beta}$ decay matrix elements persists. We find agreement with previous measurements of the 539.5- and 590.8-keV $\ensuremath{\gamma}$-ray intensities.
Structure of115Ag studied byβ−decays of115Pd and115Pdm
2012
The excited levels of ${}^{115}$Ag have been studied via the beta decay of ${}^{115}$Pd and ${}^{115}$Pd${}^{m}$. The beta-decay schemes for both states have been considerably extended, especially the scheme following the decay of ${}^{115}$Pd${}^{m}$ which was practically unknown before this work. Transition intensities and ${\mathrm{log}}_{10}ft$ values are reported, which have been missing in the literature. A set of levels around 2 MeV has been found to be strongly populated by the beta decay of the ground state of ${}^{115}$Pd and is suggested to have a three-quasiparticle nature. The properties of excited levels have been compared with the level systematics of lighter neutron-rich sil…
Consistent large-scale shell-model analysis of the two-neutrino ββ and single β branchings in 48Ca and 96Zr
2020
Abstract Two-neutrino double-beta-decay matrix elements M 2 ν and single beta-decay branching ratios were calculated for 48Ca and 96Zr in the interacting nuclear shell model using large single-particle valence spaces with well-tested two-body Hamiltonians. For 48Ca the matrix element M 2 ν = 0.0511 is obtained, which is 5.5% smaller than the previously reported value of 0.0539. For 96Zr this work reports the first large-scale shell-model calculation of the nuclear matrix element, yielding a value M 2 ν = 0.0747 with extreme single-state dominance. These matrix elements, combined with the available ββ-decay half-life data, yield effective values of the weak axial coupling which in turn are u…
β-decay studies of135–137Snusing selective resonance laser ionization techniques
2002
The decays of the very neutron rich Sn isotopes Sn135-137 were studied at CERN/ISOLDE using isotopic and isobaric selectivity achieved by the use of a resonance ionization laser ion source and mass spectroscopy, respectively. Neutron decay rates, gamma-ray singles, and gamma-gamma coincidence data were collected as a function of time. The half-life (T-1/2) and delayed neutron emission probability (P-n) values of 135 Sn were measured to be 530(20) ms and 21(3)%, respectively. For Sn-136, a T-1/2 of 250(30) ms was determined along with a P-n value of 30(5)%. For Sn-137, a T-1/2 of 190(60) ms and a P-n value of 58(15)% were deduced. Identification of low-energy transitions in Sb-135 was made p…