Search results for " Beta Decay"
showing 10 items of 323 documents
Nuclear responses for double beta decay and muon capture
2019
The existence of the neutrinoless double beta (0νββ) decay is one of the most intriguing open questions in the neutrino physics field. Despite many large-scale experiments have aimed to measure the reaction for decades, it has not yet been observed. Therefore, accurate theoretical calculations on 0νββ are crucial. To describe the double beta decay processes reliably one needs a possibility to test the involved virtual transitions against experimental data. In this work we manifest how to utilise the charge-exchange and ordinary muon capture (OMC) data in the study of 0νββ decay.The existence of the neutrinoless double beta (0νββ) decay is one of the most intriguing open questions in the neu…
Predictive flavor symmetries of the neutrino mass matrix.
2007
Here we propose an $A_4$ flavour symmetry model which implies a lower bound on the neutrinoless double beta decay rate, corresponding to an effective mass parameter $M_{ee} \gsim 0.03$ eV, and a direct correlation between the expected magnitude of CP violation in neutrino oscillations and the value of $\sin^2\theta_{13}$, as well as a nearly maximal CP phase $\delta$.
A4-based tri-bimaximal mixing within inverse and linear seesaw schemes
2009
We consider tri-bimaximal lepton mixing within low-scale seesaw schemes where light neutrino masses arise from TeV scale physics, potentially accessible at the Large Hadron Collider (LHC). Two examples are considered, based on the A4 flavor symmetry realized within the inverse or the linear seesaw mechanisms. Both are highly predictive so that in both the light neutrino sector effectively depends only on three mass parameters and one Majorana phase, with no CP violation in neutrino oscillations. We find that the linear seesaw leads to a lower bound for neutrinoless double beta decay while the inverse seesaw does not. The models also lead to potentially sizeable decay rates for lepton flavor…
Analysis of light neutrino exchange and short-range mechanisms in 0νββ decay
2020
Neutrinoless double beta decay (0νββ) is a crucial test for lepton number violation. Observation of this process would have fundamental implications for neutrino physics, theories beyond the Standard Model and cosmology. Focusing on so-called short-range operators of 0νββ and their potential interplay with the standard light Majorana neutrino exchange, we present the first complete calculation of the relevant nuclear matrix elements, performed within the interacting boson model (IBM-2). Furthermore, we calculate the relevant phase space factors using exact Dirac electron wave functions, taking into account the finite nuclear size and screening by the electron cloud. The obtained numerical r…
Energy resolution studies for NEXT
2011
This work aims to present the current state of simulations of electroluminescence (EL) produced in gas-based detectors with special interest for NEXT --- Neutrino Experiment with a Xenon TPC. NEXT is a neutrinoless double beta decay experiment, thus needs outstanding energy resolution which can be achieved by using electroluminescence. The process of light production is reviewed and properties such as EL yield and associated fluctuations, excitation and electroluminescence efficiencies, and energy resolution, are calculated. An EL production region with a 5 mm width gap between two infinite parallel planes is considered, where a uniform electric field is produced. The pressure and temperatu…
Hindered Gamow-Teller Decay to the Odd-OddN=ZGa62: Absence of Proton-NeutronT=0Condensate inA=62
2014
Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum fur Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical pred…
Renormalized Proton-Neutron Quasiparticle Random-Phase Approximation and Its Application to Double Beta Decay
1995
A self-consistent method of treating excitations of the proton-neutron quasiparticle random-phase approximation is presented. The non-self-consistent methods violate the Pauli exclusion principle and lead to an eventual collapse of the ground state. This behavior renders a reliable calculation of the nuclear matrix elements, relevant for the prediction of double-beta-decay half-lives, difficult. The present formalism promotes the Pauli exclusion principle and avoids the collapse of the double-beta-decay matrix elements. We have applied this formalism to the double beta decay of ${}^{100}$Mo.
QCD running in neutrinoless double beta decay: Short-range mechanisms
2016
16 pages.- 3 figures.- 2 tables
Effective Lagrangian approach to neutrinoless double beta decay and neutrino masses
2012
Neutrinoless double beta ($0\nu\beta\beta$) decay can in general produce electrons of either chirality, in contrast with the minimal Standard Model (SM) extension with only the addition of the Weinberg operator, which predicts two left-handed electrons in the final state. We classify the lepton number violating (LNV) effective operators with two leptons of either chirality but no quarks, ordered according to the magnitude of their contribution to \znbb decay. We point out that, for each of the three chirality assignments, $e_Le_L, e_Le_R$ and $e_Re_R$, there is only one LNV operator of the corresponding type to lowest order, and these have dimensions 5, 7 and 9, respectively. Neutrino masse…
Asymmetric tri-bi-maximal mixing and residual symmetries
2019
Asymmetric tri-bi-maximal mixing is a recently proposed, grand unified theory (GUT) based, flavor mixing scheme. In it, the charged lepton mixing is fixed by the GUT connection to down-type quarks and a $\mathcal{T}_{13}$ flavor symmetry, while neutrino mixing is assumed to be tri-bi-maximal (TBM) with one additional free phase. Here we show that this additional free phase can be fixed by the residual flavor and CP symmetries of the effective neutrino mass matrix. We discuss how those residual symmetries can be unified with $\mathcal{T}_{13}$ and identify the smallest possible unified flavor symmetries, namely $(\mathbb{Z}_{13}\times\mathbb{Z}_{13})\rtimes \mathrm{D}_{12}$ and $(\mathbb{Z}_…