Search results for "DECAY"
showing 10 items of 2087 documents
First Accurate Normalization of the β-delayed α Decay of ^{16}N and Implications for the ^{12}C(α,γ)^{16}O Astrophysical Reaction Rate.
2018
The ^{12}C(α,γ)^{16}O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced α width, γ_{11}, of the bound 1^{-} level in ^{16}O is particularly important to determine the cross section. The magnitude of γ_{11} is determined via sub-Coulomb α-transfer reactions or the β-delayed α decay of ^{16}N, but the latter approach is presently hampered by the lack of sufficiently precise data on the β-decay branching ratios. Here we report improved branching ratios for the bound 1^{-} level [b_{β,11}=(5.02±0.10)×10^{-2}] and for β-delayed α emission [b_{βα}=(1.59±0.06)×10^{-5}].…
Metals distributions within black crusts sampled on the facade of an historical monument: The case study of the Cathedral of Monza (Milan, Italy)
2019
This research deals with the characterization of black crusts collected from Dome of Monza. Black crusts (BC) can be formed as a result of different chemical and physical reactions between the stone surface and environmental factors (such as gaseous pollutants, aerosol particulate matter and its specific chemical constituents-the carbonaceous fraction and the metals); therefore, they are considered as a passive sampler of pollutants. The specific focus of the current work is the study of the metals and their distribution within the samples. To characterize BC, several techniques were used such as: HRSEM-EDX, IC and LA-ICP/MS. This integrated approach allowed us to gain information about the…
Systematic approach to β and 2vββ decays of mass A=100-136 nuclei
2015
In this work we perform a systematic study of pairs of single-β-decaying nuclei in the mass region A = 100–136 to extract information on the effective value of the axial-vector coupling constant gA. As the many-body framework we use the quasiparticle random-phase approximation (QRPA) and its proton-neutron variant (pnQRPA) in singleparticle valence bases with Woods-Saxon-calculated single-particle energies. It is found that, to a reasonable approximation, gA is a linear function of the mass number A, with a slightly different parametrization below and above the mass A = 121. Using the values of gA extracted from the linear fit, as well as an average constant value of gA, we calculate the tw…
Spectral shapes of forbidden argon β decays as background component for rare-event searches
2018
The spectral shape of the electrons from the two first-forbidden unique ${\beta }^{-}$ decays of 39Ar and 42Ar were calculated for the first time to the next-to-leading order. Especially the spectral shape of the 39Ar decay can be used to characterize this background component for dark matter searches based on argon. Alternatively, due to the low thresholds of these experiments, the spectral shape can be investigated over a wide energy range with high statistics and thus allow a sensitive comparison with the theoretical predictions, in particular at low electron energies where the shape of the computed β spectrum has a slight dependence on the value of the weak axial-vector coupling constan…
Latest results from CUPID-0
2022
International audience; CUPID-0 is a pilot experiment in scintillating cryogenic calorimetry for the search of neutrino-less double beta decay. 26 ZnSe crystals were operated continuously in the first project phase (March 2017 - December 2018), demonstrating unprecedented low levels of background in the region of interest at the Q-value of $^{82}\rm{Se}$. From this successful experience comes a demonstration of full alpha to beta/gamma background separation, the most stringent limits on the $^{82}\rm{Se}$ neutrino-less double beta decay, as well as the most precise measurement of the $^{82}$Se half-life. After a detector upgrade, CUPID-0 began its second and last phase (June 2019 - February…
β-decay half-life of V 50 calculated by the shell model
2014
In this work we survey the detectability of the β− channel of 50 23V leading to the first excited 2+ state in 50 24Cr. The electron-capture (EC) half-life corresponding to the transition of 50 23V to the first excited 2+ state in 50 22Ti had been measured earlier. Both of the mentioned transitions are 4th-forbidden non-unique. We have performed calculations of all the involved wave functions by using the nuclear shell model with the GXPF1A interaction in the full f-p shell. The computed half-life of the EC branch is in good agreement with the measured one. The predicted half-life for the β− branch is in the range ≈2 × 1019 yr whereas the present experimental lower limit is 1.5 × 1018 yr. We…
Penning-trap-assisted study of excitations in $^{88}$Br populated in β decay of $^{88}$Se
2017
Excited levels of 88Br populated in the β decay of 88Se have been studied by means of βγ and γ γ spectroscopy methods. Neutron-rich parent 88Se nuclei were produced with proton-induced fission of 238U using the Ion Guide Isotope Separator On-Line (IGISOL) method and separated from contaminants using a dipole magnet and the coupled JYFLTRAP Penning trap at the Accelerator Laboratory of the University of Jyvaskyl ¨ a. The level scheme ¨ of 88Br has been constructed and log f t values of levels were determined. The ground-state spin of 88Br is now firmly determined to be 1−. Low-energy levels in 88Br were interpreted as members of the πp3/2(νd5/2) 3, πp−1 3/2(νd5/2) 3, πf −1 5/2 (νd5/2) 3, and…
Identification of the crossing point at N=21 between normal and intruder configurations
2017
The β− decay of 34Mg was used to study the 34Al nucleus through γ spectroscopy at the Isotope Separator OnLine facility of CERN. Previous studies identified two β-decaying states in 34Al having spin-parity assignments J π = 4− dominated by the normal configuration π(d5/2) −1 ⊗ ν(f7/2) and J π = 1+ by the intruder configuration π(d5/2) −1 ⊗ ν(d3/2) −1(f7/2) 2. Their unknown ordering and relative energy have been the subject of debate for the placement of 34Al inside or outside the N = 20 “island of inversion.” We report here that the 1+ intruder lies only 46.6 keV above the 4− ground state. In addition, a new half-life of T1/2 = 44.9(4) ms, that is twice as long as the previously measured 20…
Impact of the quenching of gA on the sensitivity of 0νββ experiments
2017
Detection of the neutrinoless ββ (0νββ) decay is of high priority in the particle- and neutrino-physics communities. The detectability of this decay mode is strongly influenced by the value of the weak axial-vector coupling constant gA. The recent nuclear-model analyses of β and ββ decays suggest that the value of gA could be dramatically quenched, reaching ratios of gfree A /gA ≈ 4, where gfree A = 1.27 is the free, neutron-decay, value of gA. The effects of this quenching appear devastating for the sensitivity of the present and future 0νββ experiments since the fourth power of this ratio scales the 0νββ half-lives. This, in turn, could lead to some two orders of magnitude less sensitivit…
Second-forbidden nonunique β− decays of 24Na and 36Cl assessed by the nuclear shell model
2020
We have performed a systematic study of the log f t values, shape factors, and electron spectra for the second-forbidden nonunique β− decays of 24Na(4+) →24Mg(2+) and 36Cl(2+) →36Ar(0+) transitions under the framework of the nuclear shell model. We have performed the shell model calculations in the sd model space, using more recent microscopic effective interactions such as Daejeon16, chiral N3LO, and JISP16. These interactions are derived from the no-core shell model wave functions using Okubo-Lee-Suzuki transformation. For comparison, we have also shown the results obtain from the phenomenological USDB interaction. To test the predictive power of these interactions first we have computed …