Probing the quenching of gA by single and double beta decays

Ground-state-to-ground-state two-neutrino double beta (2νββ) decays and single beta (EC and β−) decays are studied for the A=100 (100Mo100Tc100Ru), A=116 (116Cd116In116Sn) and A=128 (128Te128I128Xe) nuclear systems by using the proton–neutron quasiparticle random-phase approximation exploiting realistic effective interactions in very large single-particle bases. The aim of this exercise is to see if both the single-beta and double-beta decay observables related to the ground states of the initial, intermediate and final nuclei participant in the decays can be described simultaneously by changing the value of the axial-vector coupling constant gA. In spite of the very different responses to single and 2νββ decays of the considered nuclear systems, the obtained results point consistently to a quenched effective value of gA that is (slightly) different for the single and 2νββ decays.Fil: Suhonen, Jouni. Universidad de Jyvaskyla; FinlandiaFil: Civitarese, Enrique Osvaldo. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Neutrino-related questions in nuclear and astro-particle physics

Since the prediction about its existence, by Pauli, the neutrino has been, and still is, the principal object in the field of nuclear, particle and astroparticle physics. Issues like its mass, oscillation parameters, the mixing with sterile species and its inclusion in cold dark matter scenarios, have raised the expectations of generations of physicists, astrophysicists and cosmologists. Without doubt, the coming years may bring a major breakthrough in neutrino physics. This is a welcome note for those which are willing to cope with the challenging and intriguing aspects of this elusive particle. Overview is given for the challenging and intriguing aspects of the neutrino physics in the context of astroparticle and cosmological studies.Departamento de Físic

Spin response of impurities in a quantum corral

In this work we investigate the dependence of spin observables, like the total spin alignment and the spin squeezing factor, for electrons confined inside an elliptic quantum corral and interacting with a pair of impurities located on the semi-major axis of the ellipse. The results suggest that such a system exhibits some of the characteristic features of a qubit, concerning the persistence of the orientation and squeezing of a component of the total spin. © 2014 World Scientific Publishing Company.Fil: Civitarese, Enrique Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Reboiro, Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Tielas, Diego Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentin

Applicability of the Richardson method in a complex-energy basis: Fermionic case

We are testing the applicability of the algebraic procedure developed by Richardson for bound states to solve the pairing-force problem in presence of states with complex energies. This scenario, in which nucleons occupy single-particle states with complex energies and interact via the pairing force, is closely related to the microscopic description of nuclei with a large neutron (or proton) excess in basis which includes single-particle resonances. It is shown that the method gives results which are in good agreement with exact solutions. This finding is in coincidence with previously published works, by other authors, based on different methods to describe resonances.Fil: Civitarese, Enrique Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Reboiro, Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Tielas, Diego Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentin

Nuclear and weak interaction aspects of neutrinoless double beta decay: Recent results

The determination of the value of the light neutrino mass, as well as the determination of the nature of the neutrino, are two of the fundamental questions which motivate the experimental search of signals of neutrinoless double beta decay transitions. Here, we shall review some of the the essentials of the theory, based on both nuclear structure and elementary particle physics, relevant for the understanding of the problem.Facultad de Ciencias Exacta

Probing the quenching of gA by single and double beta decays

Ground-state-to-ground-state two-neutrino double beta (2νββ) decays and single beta (EC and β−) decays are studied for the A=100 (100Mo100Tc100Ru), A=116 (116Cd116In116Sn) and A=128 (128Te128I128Xe) nuclear systems by using the proton–neutron quasiparticle random-phase approximation exploiting realistic effective interactions in very large single-particle bases. The aim of this exercise is to see if both the single-beta and double-beta decay observables related to the ground states of the initial, intermediate and final nuclei participant in the decays can be described simultaneously by changing the value of the axial-vector coupling constant gA. In spite of the very different responses to single and 2νββ decays of the considered nuclear systems, the obtained results point consistently to a quenched effective value of gA that is (slightly) different for the single and 2νββ decays.Facultad de Ciencias Exacta

Multipole decomposition of the cross section of the neutrino-lead scattering process 208Pb(g.s.)(ν,ν)208Pb∗

We calculate neutral-current contributions to the process ν+208Pb(g.s)→ ν′+208Pb∗, for incoming neutrino energies up to 150 MeV. The spectrum of 208Pb is calculated by performing a diagonalization of the δ-force interaction in the space of particle-hole pairs, both for neutrons and protons. We study the dependence of the cross section on the energy of the neutrino and present its multipole decomposition for normal and abnormal parity states. We compare our results to the estimate of neutral-current contributions by other authors, and to our previous results for the charged-current channel.Instituto de Física La Plat

Analyticity of the time dependence of resonance poles: Solving the Friedrichs model with a time-dependent interaction

We extend the standard Friedrichs model with an extra term that includes time-dependent interactions. The time dependence of the poles of the reduced resolvent of the model is explicitly calculated. It is found that these poles behave as analytical functions of the added time-dependent interaction. The present results are compared with the ones reported by Kälbermann, concerning the assisted tunnelling of α particles. © 2012 American Physical Society.Facultad de Ciencias ExactasConsejo Nacional de Investigaciones Científicas y Técnica

On the definition of entropy for quantum unstable states

The concept of entropy is central to the formulation of the quantum statistical mechanics, and it is linked to the definition of the density operator and the associated probabilities of occupation of quantum states. The extension of this scheme to accommodate for quantum decaying states is conceptually difficult, because of the nature of these states. Here we present a way to treat quantum unstable states in the context of statistical mechanics. We focuss on the definition of the entropy and avoid the use of complex temperatures.Facultad de Ciencias Exacta

Probing the quenching of gA by single and double beta decays

Ground-state-to-ground-state two-neutrino double beta (2νββ) decays and single beta (EC and β−) decays are studied for the A=100 (100Mo100Tc100Ru), A=116 (116Cd116In116Sn) and A=128 (128Te128I128Xe) nuclear systems by using the proton–neutron quasiparticle random-phase approximation exploiting realistic effective interactions in very large single-particle bases. The aim of this exercise is to see if both the single-beta and double-beta decay observables related to the ground states of the initial, intermediate and final nuclei participant in the decays can be described simultaneously by changing the value of the axial-vector coupling constant gA. In spite of the very different responses to single and 2νββ decays of the considered nuclear systems, the obtained results point consistently to a quenched effective value of gA that is (slightly) different for the single and 2νββ decays.Facultad de Ciencias Exacta