Search results for "Fermi"
showing 10 items of 1388 documents
Resonant enhancement of neutrinoless double-electron capture in 152Gd.
2010
In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the ${Q}_{ϵϵ}$ value between the ground states of $^{152}\mathrm{Gd}$ and $^{152}\mathrm{Sm}$ by Penning-trap mass-ratio measurements. The new ${Q}_{ϵϵ}$ value of 55.70(18) keV results in a half-life of ${10}^{26}\text{ }\text{ }\mathrm{yr}$ for a 1 eV neutrino mass. With this smallest half-life among known $0\ensuremath{\nu}ϵϵ$ transitions, $^{152}\mathrm{Gd}$ is a promising candidate for the search for neutrinoless double-electron capture.
Corrections for positon annihilation in flight in nuclear spectrometry
1973
Abstract Theories of positon single- and two-quanta annihilation in flight, the Fermi beta-decay theory, and theories of positon energy loss are used in calculations of total probabilities of annihilation in flight of positons in continuous spectra. The results are given in a nomogram useful in correcting for positon annihilation in flight in various nuclear-spectrometry experiments. Confirmation of the theoretical basis employed was obtained by comparing total absolute probabilities for annihilation in flight of 62 Cu positons in Perspex, copper, cadmium and lead, using a new differential method. The agreement with the theory was found to be excellent. A method for obtaining “correct” posi…
Elliptic and Hexadecapole Flow of Charged Hadrons inAu+AuCollisions atsNN=200 GeV
2010
Differential measurements of the elliptic (upsilon(2)) and hexadecapole (upsilon(4)) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p(T)) and collision centrality or number of participant nucleons (N-part) for Au + Au collisions at root s(NN) = 200 GeV/ The upsilon(2,4) measurements at pseudorapidity vertical bar eta vertical bar <= 0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0 < vertical bar eta vertical bar < 3.9, show good agreement, indicating the absence of significant Delta eta-dependent nonflow correlations. Sizable values for upsilon(4)(p(T)) are observed with a ratio upsilon(4)(p(T), N-part)/…
Nuclear levels of 183W studied with and reactions
2011
Abstract The level structure of 183 W has been studied using gamma–gamma coincidences from thermal neutron capture in 182 W accompanied with the reaction ( d → , p ) . From these data and those of previous studies a total of 76 levels and about 490 connecting γ -transitions have been established for energies below 2.4 MeV. An analysis based on the standard distorted-wave Born approximation (DWBA) provides the lj -angular momentum transfers and spectroscopic factors for 36 levels up to 2.2 MeV excitation energy. A large number of particle transitions indicate an influence of strong mixing between particle and probably hole states. The extra exchange of phonons across the Fermi surface leads …
Production of hypernuclei in multifragmentation of nuclear spectator matter
2007
In peripheral collisions of relativistic heavy ions highly excited spectators containing Lambda-hyperons can be produced. Such strange spectator matter may undergo a break-up into many fragments (multifragmentation) as it is well established for ordinary nuclear systems. We generalize the statistical multifragmentation model, previously successfully used for the description of experimental data, for the case of hypernuclear systems. We predict relative yields of hypernuclei and the main characteristics of such a break-up. We point at a connection of this phenomenon with a liquid-gas phase transition in hypermatter.
Nuclear structure of 187W studied with (n,γ) and (d,p) reactions
2008
Abstract The level structure of 187 W has been studied using prompt and delayed gamma–gamma coincidences from thermal neutron capture in 186 W and also measuring the ( d , p ) reaction. From these data and those of previous studies a total of 170 levels (121 connected by γ transitions) have been established for energies below 2.35 MeV. Some of these levels have been grouped into rotational bands built on 14 intrinsic states of quasi-particle and quasi-particle plus phonon character. Of particular interest has been the identification of “quasi bands” with inverse spin sequence based on the newly established isomeric 11 / 2 + state at 410.1 keV. Although the DWBA analysis permitted definite s…
Low-spin mixed particle–hole structures in 185W
2005
Abstract The level structure of 185W has been studied using the prompt and delayed gamma–gamma coincidences from thermal neutron capture in 184W accompanied with the one-nucleon transfer reactions ( d , p ) and ( d , t ) with polarized beams. From these data and those of previous studies a total of 183 levels has been established for energies below 3 MeV. Many of these states have been grouped into rotational bands built on 28 intrinsic states of quasiparticle and quasiparticle-plus-phonon character. Although the DWBA analysis permitted definite spin–parity assignments for most of states a large number of particle transitions have ‘anomalous’ angular and asymmetry shapes with respect to the…
High-spin states in205Rn:A new shears band structure?
1999
The high-spin structure of {sup 205}Rn has been investigated for the first time following the {sup 170}Er({sup 40}Ar,5n) and {sup 197}Au({sup 14}N,6n) reactions at beam energies of 183 MeV and 90{endash}110 MeV, respectively, using the Jurosphere and YRAST Ball arrays. Two new cascades have been identified which dominate the high-spin decay. One of these, consisting of ten stretched M1 transitions with unobserved E2 crossover transitions, is interpreted as a shears structure based on the {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}i{sub 13/2}{sup 2} (or {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}h{sub 9/2}i{sub 13/2}) configuration. {copyright} {ital 1999} {ital The American Physical…
Search for a 2-quasiparticle high-Kisomer inRf256
2011
The energies of 2-quasiparticle (2-qp) states in heavy shell-stabilized nuclei provide information on the single-particle states that are responsible for the stability of superheavy nuclei. We have calculated the energies of 2-qp states in {sup 256}Rf, which suggest that a long-lived, low-energy 8{sup -} isomer should exist. A search was conducted for this isomer through a calorimetric conversion electron signal, sandwiched in time between implantation of a {sup 256}Rf nucleus and its fission decay, all within the same pixel of a double-sided Si strip detector. A 17(5)-{mu}s isomer was identified. However, its low population, {approx}5(2)% that of the ground state instead of the expected {a…
Research on exotic nuclei-experiments at the limits of the nuclear landscape
1999
Experimental progress in studies of exotic nuclei and decay modes near the proton drip line and near the boundary of known neutron-rich nuclei is reviewed with emphasis on recent developments in detector systems and separation techniques.