Search results for " Beta Decay"
showing 10 items of 323 documents
Signatures of oblate deformation in the ^{111}Tc nucleus
2011
Monoisotopic samples of exotic, neutron-rich ${}^{111}$Mo nuclei, produced in the deuteron-induced fission of ${}^{238}$U and separated using the IGISOL3 isotope separator, coupled to the JYFLTRAP Penning trap, were used to perform $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-coincidence spectroscopy of ${}^{111}$Tc. New excited levels in ${}^{111}$Tc populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{111}$Mo provide the first indication for an oblate deformation in the mass $A\ensuremath{\approx}110$ region. The wide spin range of levels populated in ${}^{111}$Tc following the decay of ${}^{111}$Mo indicates the existence of two $\ensuremath{\beta}$-decaying levels in ${…
Schematic and realistic model calculations of the isovector spin monopole excitations in 116In
2012
The excitation of Gamow-Teller (GT) and isovector spin monopole (IVSM) Jπ=1+ modes in 116In by (p,n) and (n,p) charge-exchange reactions on 116Cd and on 116Sn, respectively, is studied within the framework of the quasiparticle random-phase approximation. The calculations have been performed both for schematic and realistic model situations. It appears that the calculated admixture of the IVSM and Gamow-Teller (GT) Jπ=1+ excitations is negligible and that the contribution to the strength above 20 MeV of excitation energy, in 116In, is due to the IVSM (σr2t ±) mode. This result is compared with the recent experimental work that reported a large amount of both (p,n) and (n,p) strength beyond 1…
Total absorption γ-ray spectroscopy of beta delayed neutron emitters
2013
Preliminary results of the data analysis of the beta decay of 94Rb using a novel - segmented- total absorption spectrometer are shown in this contribution. This result is part of a systematic study of important contributors to the decay heat problem in nuclear reactors. In this particular case the goal is to determine the beta intensity distribution below the neutron separation energy and the gamma/beta competition above.
Double charge exchange reactions as a probe for neutrinoless double beta decay nuclear matrix elements
2020
Abstract The formalism to describe heavy-ion double charge exchange (DCE) processes in the eikonal and small-momentum transfer approximations introduced in Phys. Rev. C 98, 061601(R) (2018) is briefly discussed. It is also shown that, under the previous approximations, the heavy-ion DCE cross-section can be factorized in terms of a reaction and a nuclear part. A double charge exchange effective potential is explicitly derived in the closure approximation and also for the first time the explicit form of the DCE nuclear matrix elements, that are of the form of double Gamow-Teller and double Fermi. The recent hypothesis of a linear correlation between double Gamow-Teller neutrinoless double be…
Massive neutrinos and right-handed weak currents in double beta decay.
1993
The contributions of right-handed weak currents in neutrinoless double beta decay are studied taking explicitly into account the mass corrections to the intermediate neutrino propagator. Due to these corrections the right-handed currents become effective even if all neutrinos are light ([ital m][sub [nu]][gt]10 MeV). Explicit expressions for the neutrino-momentum integrals and the decay half-life are derived. As an example two neutrino-mass scenarios containing the hypothetical 17-keV neutrino are discussed. The experimental half-life of the [sup 76]Ge[r arrow][sup 76]Se decay is used to obtain an upper limit for a new kind of effective right-handed coupling within the two scenarios.
Weak-interaction and nuclear-structure aspects of nuclear double beta decay
1998
Abstract Weak-interaction and nuclear-structure aspects of double beta decay are reviewed. Starting from effective electroweak lagrangians, decay rates for the two-neutrino and neutrinoless modes of the nuclear double beta decay transitions are defined and second-order perturbative expressions for the nuclear decay amplitudes are given. Nuclear matrix elements of the relevant operators are presented, as extracted from data and from shell-model and QRPA calculations as well as from other theoretical approximations. The analysis is performed both for the two-neutrino and neutrinoless modes of the decay. The expressions for ground-state-to-ground-state and ground-state-to-excited-state transit…
Penning-trap-assisted study of 115Ru beta decay
2011
The beta decay of 115Ru has been studied by means of Penning-trap-assisted beta and gamma spectroscopy at the IGISOL facility. The level scheme of 115Rh has been substantially extended and compared with the level systematics of lighter rhodium isotopes. Tentative candidates for three states of the deformed K = 1/2 band have been suggested. The beta-strength distribution of the beta decay of 115Ru differs from the beta decays of 111, 113, 113mRu isotopes due to non-observation of the 3-quasiparticle states in 115Rh. The decay properties of 115Ru indicate a spin-parity of (3/2+ for its beta-decaying ground state. In addition, possible Nilsson states as well as the shape and spin transitions i…
Questioning model-independent estimates of 2 νββ decay rates
2000
Abstract In this work we discuss the validity of recently published results, by Rumyantsev and Urin, concerning nuclear matrix elements of the two-neutrino double-beta decay transitions. These authors claim that these matrix elements can be calculated in a model-independent way. We have re-analyzed their results and extended their formalism to account for proton-neutron correlations at the QRPA level of approximation. We have found that the formalism fails in describing the double beta decay observables.
Qvalue and half-life of double-electron capture in184Os
2012
The observation of neutrinoless double-beta transitionswould reveal physics beyond the Standard Model, asit would establish neutrinos to be Majorana particles,which implies a violation of the lepton number conserva-tion. Experiments searching for these transitions have fo-cused on the detection of neutrinoless double-beta decay(0 ) rather than neutrinoless double-electron capture(0). One reason among others is in general the sig-ni cantly shorter half-life of the 0 process. However,in the case of neutrinoless double-electron capture, thetransition is expected to be resonantly enhanced if theinitial and the nal state of the transition are degeneratein energy [1{3].In this work, we inves…
Microscopic study of muon-capture transitions in nuclei involved in double-beta-decay processes
2003
Abstract Total and partial ordinary muon-capture (OMC) rates to 1 + and 2 − states are calculated in the framework of the proton–neutron quasiparticle random-phase approximation (pnQRPA) for several nuclei involved in double-beta-decay processes. The aim is to obtain information on intermediate states involved in double-beta-decay transitions having these nuclei as either daughter or parent nuclei. It is found that the OMC observables, just like the 2 νββ -decay amplitudes, strongly depend on the particle–particle part of the proton–neutron interaction. First experiments measuring the partial OMC rates for nuclei involved in double beta decays have recently been performed.