Search results for "theoretical nuclear physics"
showing 10 items of 20 documents
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) J π = 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) J π = 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 be…
Nuclear matrix elements for resonant neutrinoless double electron capture
2012
The resonant neutrinoless double electron-capture (R0νECEC) is discussed from the point of view of the resonance condition and the involved nuclear matrix elements. A brief outline of the involved theory framework is given. The present status of measurements of the involved atomic masses and possible R0νECEC candidates is reviewed. peerReviewed
Theoretical investigation of the double-beta processes in 96Ru
2012
The two-neutrino (2ν2β) and neutrinoless (0ν2β) double-β decays of 96Ru are investigated for the transitions to the ground state, 0+ gs, and 0+ and 2+ excited states in 96Mo by using the quasiparticle random-phase approximation combined with the multiple-commutator model. G-matrix-based nuclear forces are used in realistic single-particle model spaces. All the possible channels, β+β+, β+EC, and ECEC, are discussed for both the 2ν2β and 0ν2β decays. The associated half-lives are computed, in particular the one corresponding to the resonant neutrinoless double electron capture (R0νECEC) transition to the 2.712.68-MeV nuclear state in 96Mo. This work represents the most complete theoretical in…
Search for double-\beta decay of \{106}Cd by using isotopically enriched \{106}CdWO_{4} crystal scintillator
2012
A search for double β processes in 106Cd was carried out at the Gran Sasso National Laboratories of the INFN (Italy) by using a CdWO4 crystal scintillator (mass of 215 g) enriched in 106Cd up to 66%. After 6590 h of data taking, half-life limits on double beta processes in 106Cd were set at level of 1019 −1021 yr. A possible resonant enhancement of the 0ν2ε processes has also been estimated in the framework of the QRPA approach. peerReviewed
Search for double-\beta decay processes in \{106}Cd with the help of a \{106}CdWO_{4} crystal scintillator
2012
A search for double β processes in 106Cd was carried out at the Gran Sasso National Laboratories of the INFN (Italy) with the help of a 106CdWO4 crystal scintillator (215 g) enriched in 106Cd up to 66%. After 6590 h of data taking, new improved half-life limits on the double β decay processes in 106Cd were established at the level of 1019–1021 yr; in particular, T 2νεβ+ 1/2 2.1 × 1020 yr, T 2ν2β+ 1/2 4.3 × 1020 yr, and T 0ν2ε 1/2 1.0 × 1021 yr. The resonant neutrinoless double-electron captures to the 2718-, 2741-, and 2748-keV excited states of 106Pd are restricted to T 0ν2K 1/2 4.3 × 1020 yr, T 0νKL1 1/2 9.5 × 1020 yr, and T 0νKL3 1/2 4.3 × 1020 yr, respectively (all limits at 90% confide…
Precision Mass Measurements beyond $^{132}$Sn: Anomalous behaviour of odd-even staggering of binding energies
2012
Atomic masses of the neutron-rich isotopes $^{121-128}$Cd, $^{129,131}$In, $^{130-135}$Sn, $^{131-136}$Sb, and $^{132-140}$Te have been measured with high precision (10 ppb) using the Penning trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei $^{135}$Sn, $^{136}$Sb, and $^{139,140}$Te were measured for the first time. The data reveals a strong $N$=82 shell gap at $Z$=50 but indicates the importance of correlations for $Z>50$. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N$=82 for Sn, with the $Z$-dependence that is unexplainable by the current theoretical models.
Rare beta decays and the spectrum-shape method
2017
This is a thesis consisting of seven publications and an introductory part on theoretical studies on rare single beta decays. Firstly, the theoretical framework is applied to the computation of partial half-lives for few selected cases of rare single beta-decay transitions. This includes the study on a possible ultra-low-Q-value decay branch of 115Cd as well as the highly forbidden beta decays of 48Ca and 50V. The double magic 48Ca is one of the few experimentally verified nuclei that decay via the two-neutrino mode of double beta decay. A theoretical study on the single beta-decay branches was used to inspect the competition between the single and double beta-decay channels. In the case of…
Unified description of 2+_1 states within the deformed quasiparticle random-phase approximation
2013
We describe low-lying collective states in deformed even-even nuclei within a deformed quasiparticle randomphase approximation (dQRPA) by using a single-particle basis with good angular momentum. The statistical factors, accounting for the level occupancy, appear in the dQRPA in a natural way as rotation coefficients that take the intrinsic system to the laboratory system. We have used our model by performing a systematic analysis of E2 transitions from the first 2+ state to the ground state for all superfluid nuclei in the range 50 < Z 100 by using a common charge polarization parameter χ = 0.2. In spite of its similarity to the QRPA, this method is able to describe in an unified way gross…
Analysis of double-beta transitions in 78^Kr
2013
In this paper a comprehensive theoretical analysis of the two-neutrino (2ν2β) and neutrinoless (0ν2β) doublebeta decays of 78Kr is performed by evaluating the corresponding nuclear matrix elements by combining the quasiparticle random-phase approximation with the multiple-commutator model. Transitions to the ground state 0+ gs and 0+ and 2+ excited states in 78Se are investigated by using G-matrix-based nuclear forces. The channels β+β+, β+EC, and ECEC are discussed for the 2ν2β decays and the channels β+β+ and β+EC for the 0ν2β decays. The associated half-lives are computed to see if the detection of some of these transitions is experimentally feasible. peerReviewed
Neutrinoless double beta-plus/EC decays
2013
The relation of neutrino masses to neutrino oscillations and the nuclear double beta decay is highlighted. In particular, the neutrinoless 𝛽+ 𝛽+, 𝛽+EC, and resonant ECEC decays are investigated using microscopic nuclear models. Transitions to the ground state and excited 0+ states are analyzed. Systematics of the related nuclear matrix elements are studied and the present status of the resonant ECEC decays is reviewed. peerReviewed