Search results for "Decay"
showing 10 items of 2087 documents
Lepton conservation and time reversal in β-decay
1959
It was investigated which conclusions can be inferred from β-decay experiments taking into account experimental errors but without making theoretical assumptions.
Nuclear matrix elements and the neutrinoless double beta decay
2005
Systematics of the nuclear matrix elements related to the neutrinoless double beta ( 0 ν β β ) decay are discussed. The calculation of the related nuclear matrix elements in the framework of the proton-neutron quasiparticle random-phase approximation (pnQRPA) is analyzed. In particular, the extraction of a proper value of the proton-neutron particle-particle interaction parameter in this theory is addressed. The relevance of different multipoles in the multipole decomposition of the 0 ν β β matrix element is also discussed.
η→π0γγdecay within a chiral unitary approach revisited
2008
In view of the recent experimental developments in η→π^(0)γ γ decay, and the fact that the Particle Data Group in the online edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of E. Oset, J. R. Pelaez, and L. Roca [Phys. Rev. D 67, 073013 (2003)], a reevaluation of the decay width of the in this channel has been done, reducing its uncertainty by almost a factor of 2. The new input of the Particle Data Group is used, and invariant mass distributions and total widths are compared with the most recent results from the AGS and MAMI experiments, and preliminary ones of KLOE. The agreement of the theory with the AGS…
Two neutral pion photoproduction off the proton between threshold and 800 MeV
1997
Abstract The photoproduction of two neutral pions off the proton has been studied for incident photon energies between E γ = 309 MeV (threshold) and 792 MeV with the TAPS photon spectrometer at the Mainz Microtron MAMI. Both 3γ- and 4γ-events have been analysed in order to deduce the total p ( γ , 2 π 0 ) p cross section. The total cross section is less than 300 nb between threshold and ⋍ 460 MeV, beyond which it starts to rise to a maximum value of about 11 μb at around 750 MeV. For the highest energies it starts to decrease again. The 4γ-sample has been used to reconstruct 2 neutral pions from the above reaction channel by an invariant mass and a missing mass analysis. After reconstructio…
Description of the two-neutrino ββ decay of100Mo by pnMAVA
2009
The microscopic anharmonic vibrator approach (MAVA) is a scheme where the one- and two-phonon states of an even–even nucleus are treated consistently by using a realistic microscopic nuclear Hamiltonian. This model has recently been extended to describe odd–odd nuclei by adding proton–neutron phonons in a scheme called the proton–neutron MAVA (pnMAVA). In this paper, we apply pnMAVA to compute the nuclear matrix elements corresponding to the two-neutrino double beta (2νββ) decay of 100Mo to the ground state and the first excited 0+ state of 100Ru in a realistic single-particle space. We also compute the GT− and GT+ Gamow–Teller strength functions and compare them with the plain pnQRPA (prot…
Perturbative analysis of the 2νββ decays of 100Mo and 116Cd
2003
We have performed a theoretical analysis of the ground-state-to-ground-state transitions in 100Mo and 116Cd, based on the quasiparticle random-phase approximation and on a straightforward perturbative scheme. The results show that the single-state dominance found in the realistic calculations of the nuclear matrix elements, which is consistent with data, can be viewed as a result of the interference between few two-quasiparticle configurations.
Evidence for oblate structure inPb186
2005
In-beam $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence data have been collected for $^{186}\mathrm{Pb}$ by combining the JUROGAM Ge-detector array and the GREAT spectrometer with the RITU gas-filled recoil separator for recoil-decay tagging measurements. In addition to the known prolate yrast band in $^{186}\mathrm{Pb}$, these data have enabled a new low-lying side band to be identified. Based on the analysis of its decay pattern and comparison with Interacting Boson Model (IBM) calculations, the new band is associated with an oblate shape.
Estimation of bounds for left-right mixing from nuclear double beta decay processes
1993
Abstract Nuclear matrix elements, extracted from a systematic calculation of neutrinoless double beta decay rates for 0 + g.s →o + g.s transitions in 76 Ge, 82 Se, 128 Te, 130 Te and 136 Xe, have been used to compute bounds on the left-right mixing angle ζ of the weak currents. The parameters of the nuclear model have been fixed by calculating the corresponding two-neutrino double beta decay half lives. The present analysis favours a mixing of the order of |tanξ| −3 which is to be compared with those obtained in muon decay (|tan ξ | ⩽ 0.035) and in supernova (|tan ξ | ⩽ 10 −5 ) analysis. It shows that nuclear structure calculations yield estimates on ξ which complement the existing data.
TAS measurements for reactor physics and nuclear structure
2011
In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
The probability of prompt and delayed fission of muonic237Np
1991
Fission fragments from the reaction237Np(μ−,γ,f) have been measured in coincidence with muonic X-rays. The efficiency of the fission fragment detector is determined from (μ−,γ,f)-data of the same experiment. The total fission probability perμ-stopPt has been measured as well as the fission probabilities Pf of the non-radiative muonic (3d→1s)- and (2p→1s)-transitions; the latter has been divided into two parts leading to different mean excitation energiesE:P t =(54±17)%,P f (3d→1s)=(41±21)%,P f (2p→1s,E=6.218 MeV)=(61±19)%, andP f (2p→1s,E=6.525 MeV)=(57±18)%. The influence of the muon on the fission barrier is discussed. The fission probability after muon capture is compared with a calculat…