Search results for "radioactive decay"
showing 10 items of 190 documents
Measurement of the double-βdecay half-life ofNd150and search for neutrinoless decay modes with the NEMO-3 detector
2009
The half-life for double-{beta} decay of {sup 150}Nd has been measured by the NEMO-3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of {sup 150}Nd, we measured the half-life for 2{nu}{beta}{beta} decay to be T{sub 1/2}{sup 2{nu}}=(9.11{sub -0.22}{sup +0.25}(stat.){+-}0.63(syst.))x10{sup 18} yr. The observed limit on the half-life for neutrinoless double-{beta} decay is found to be T{sub 1/2}{sup 0{nu}}>1.8x10{sup 22} yr at 90% confidence level. This translates into a limit on the effective Majorana neutrino mass of <4.0-6.3 eV if the nuclear deformation is taken into account. We also set limits on models involving Majoron emission, right-hand…
New precise measurements of the and decay asymmetries
2010
Abstract The decay asymmetries of the weak radiative hyperon decays Ξ 0 → Λ γ and Ξ 0 → Σ 0 γ have been measured with high precision using data of the NA48/1 experiment at CERN. From about 52 000 Ξ 0 → Λ γ and 15 000 Ξ 0 → Σ 0 γ decays, we obtain for the decay asymmetries α Ξ 0 → Λ γ = − 0.704 ± 0.019 stat ± 0.064 syst and α Ξ 0 → Σ 0 γ = − 0.729 ± 0.030 stat ± 0.076 syst , respectively. These results are in good agreement with previous experiments, but more precise.
STATISTICAL DECAY OF EXCITED ΛΛ HYPERNUCLEI AND γ-SPECTROSCOPY AT $\rm \bar P \rm ANDA$
2009
Hypernuclear physics is currently attracting renewed attention. Thanks to the use of stored [Formula: see text] beams, copious production of double Λ hypernuclei is expected at the [Formula: see text] experiment which will enable high precision γ-spectroscopy of such nuclei for the first time. In the present work we have studied the population of particle stable, excited states in double hypernuclei after the capture of a Ξ- within a statistical decay model. In order to check the feasibility of producing and performing γ-spectroscopy of double hypernuclei at [Formula: see text], an event generator based on these calculations has been implemented in the [Formula: see text] simulation framew…
Neutron and proton spectra from the decay ofΛhypernuclei
1997
We have determined the spectra of neutrons and protons following the decay of {Lambda} hypernuclei through the one- and two-nucleon-induced mechanisms. The momentum distributions of the primary nucleons are calculated and a Monte Carlo simulation is used to account for final state interactions. The shape of the proton spectrum is sensitive to the value of {Gamma}{sub n}/{Gamma}{sub p} the ratio of neutron- to proton-induced decay, and the available experimental information favors larger values than those predicted by the one-pion-exchange model. From the spectra we calculate the number of neutrons (N{sub n}) and protons (N{sub p}) per {Lambda} decay and show how the measurement of these qua…
Opening of the Z=40 subshell gap and the double-beta decay of 100Mo
2002
Abstract Experimental and theoretical study of the β − decay of 100 Nb to the two-quasiparticle states in 100 Mo suggests the opening of the Z =40 subshell gap in the proton pf-0g 9/2 shell for isobars near 100 Mo. Assuming the opening of the Z =40 subshell gap both for 100 Mo and 100 Ru enables the study of the effects of this subshell gap upon the two-neutrino and neutrinoless double-beta-decay rates of 100 Mo to the ground state and excited states in 100 Ru. It is found that the influence of the opening of the Z =40 gap has very minor effects on the beta-decay and double-beta-decay feeding of the 0 + and 2 + states of 100 Ru.
Identification of low-lying proton-based intruder states in189–193Pb
2002
Low-lying proton-based intruder states have been observed in the odd-mass isotopes Pb-189,Pb-191,Pb-193 in experiments at the RITU gas-filled recoil separator. The identification has been performed ...
β−-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes
2009
The low-lying structure of W-188,W-190,W-192 has been studied following beta decays of the neutron-rich mother nuclei Ta-188,Ta-190,Ta-192 produced following the projectile fragmentation of a 1-GeV-per-nucleon Pb-208 primary beam on a natural beryllium target at the GSI Fragment Separator. The beta-decay half-lives of Ta-188, Ta-190, and Ta-192 have been measured, with gamma-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion beta-gamma correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in W-188, W-190, and W-192, which highlight a change in nuclear shape at W-190 compared with that of …
Identification of excited states in doubly odd63140Eu77by recoil-isomer tagging
2002
The 36Ar + 107Ag fusion-evapn. reaction was used to search for isomeric states in the N = 77 isotope 140Eu near the proton-drip line. The recoiling nuclei were implanted into a Si detector, at the focal plane of a gas-filled separator, where prompt and delayed g-ray transitions were correlated across isomeric states using recoil-isomer tagging. The feeding and decay of a new 299(3) ns isomeric state was established. This measurement represents the first observation of excited high-spin states in 140Eu. The behavior of the new states above the isomer is discussed in terms of theor. calcns. based upon the cranked-shell model and upon the exptl. systematics of other N = 77 isotones. Within thi…
Observation of a dramatic hindrance of the nuclear decay of isomeric states for fully ionized atoms
2003
Abstract The half-lives of isomeric states of fully ionized 144Tb, 149Dy and 151Er have been measured. These nuclides were produced via fragmentation of about 900 MeV/u 209Bi projectiles, separated in flight with the fragment separator (FRS) and stored in the cooler ring (ESR). The decay times of the cooled fragments have been measured with time-resolved Schottky spectrometry. We observed for the first time drastic increases of the half-lives of bare isomers by factors of up to 30 compared to their neutral counterparts. This is due to the exclusion of the strong internal conversion and electron-capture channels in the radioactive decay of these bare nuclei. The experimental results are in g…
Recoil decay tagging ofγrays in the extremely neutron-deficient nucleusOs162
2004
The neutron-deficient nucleus $^{162}\mathrm{Os}$, produced in the $^{106}\mathrm{Cd}(^{58}\mathrm{Ni},2n)$ reaction, has been studied using the JUROGAM $\ensuremath{\gamma}$-ray spectrometer in conjunction with the RITU gas-filled separator and the GREAT focal plane spectrometer. $\ensuremath{\gamma}$-ray transitions in $^{162}\mathrm{Os}$ have been assigned for the first time through the application of the recoil decay tagging technique. The excitation energy of the ${2}^{+}$ state and the tentative energy of the ${8}^{+}$ state are discussed in terms of the systematic energy trends as the $N=82$ shell gap is approached.