275 research outputs found
Branching ratios for the beta decay of 21Na
We have measured the beta-decay branching ratio for the transition from 21Na
to the first excited state of 21Ne. A recently published test of the standard
model, which was based on a measurement of the beta-nu correlation in the decay
of 21Na, depended on this branching ratio. However, until now only relatively
imprecise (and, in some cases, contradictory) values existed for it. Our new
result, 4.74(4)%, reduces but does not remove the reported discrepancy with the
standard model.Comment: Revtex4, 2 fig
Peripheral elastic and inelastic scattering of O 17 , 18 on light targets at 12 MeV/nucleon
A study of interaction of neutron rich oxygen isotopes O with light
targets has been undertaken in order to determine the optical potentials needed
for the transfer reaction C(O,O)C. Optical
potentials in both incoming and outgoing channels have been determined in a
single experiment. This transfer reaction was used to infer the direct capture
rate to the F(p,)Ne which is essential to estimate the
production of F at stellar energies in ONe novae. The success of the
asymptotic normalization coefficient (ANC) as indirect method for astrophysics
is guaranteed if the reaction mechanism is peripheral and the DWBA cross
section calculations are warranted and stable against OMP used. We demonstrate
the stability of the ANC method and OMP results using good quality elastic and
inelastic scattering data with stable beams before extending the procedures to
rare ion beams. The peripherality of our reaction is inferred from a
semiclassical decomposition of the total scattering amplitude into barrier and
internal barrier components.
Comparison between elastic scattering of O, O and O
projectiles is made.Comment: 14 pages, 19 figure
Expanding RIB Capabilities at the Cyclotron Institute: \textsuperscript{3}He-LIG production with an Isobar Separator LSTAR
A new \textsuperscript{3}He-driven IGISOL production station and mass
separator have been designed to produce neutron-deficient low-mass isotopes at
the Cyclotron Institute for the TAMUTRAP facility. The LSTAR design has a mass
resolution to reject contaminants with
efficiency.Comment: Proceeding for EMIS 202
Experimental Validation of the Largest Calculated Isospin-Symmetry-Breaking Effect in a Superallowed Fermi Decay
A precision measurement of the gamma yields following the beta decay of 32Cl
has determined its isobaric analogue branch to be (22.47^{+0.21}_{-0.19})%.
Since it is an almost pure Fermi decay, we can also determine the amount of
isospin-symmetry breaking in this superallowed transition. We find a very large
value, delta_C=5.3(9)%, in agreement with a shell-model calculation. This
result sets a benchmark for isospin-symmetry-breaking calculations and lends
support for similarly-calculated, yet smaller, corrections that are currently
applied to 0+ -> 0+ transitions for tests of the Standard Model
Scattering of Be and B and the astrophysical S factor
Measurements of scattering of Be at 87 MeV on a melamine (CNH) target and of B at 95 MeV on C were performed. For Be
the angular range was extended over previous measurements and monitoring of the
intensity of the radioactive beam was improved. The measurements allowed us to
check and improve the optical model potentials used in the incoming and
outgoing channels for the analysis of existing data on the proton transfer
reaction N(Be,B)C. The resultslead to an updated
determination of the asymptotic normalization coefficient for the virtual decay
B Be + . We find a slightly larger value,
fm, for the melamine target. This
implies an astrophysical factor, eVb, for the
solar neutrino generating reaction Be(,)B.Comment: 7 pages, 4 figure
Astrophysical S factor for the radiative capture 12N(p,gamma)13O determined from the 14N(12N,13O)13C proton transfer reaction
The cross section of the radiative proton capture reaction on the drip line
nucleus 12N was investigated using the Asymptotic Normalization Coefficient
(ANC) method. We have used the 14N(12N,13O)13C proton transfer reaction at 12
MeV/nucleon to extract the ANC for 13O -> 12N + p and calculate from it the
direct component of the astrophysical S factor of the 12N(p,gamma)13O reaction.
The optical potentials used and the DWBA analysis of the proton transfer
reaction are discussed. For the entrance channel, the optical potential was
inferred from an elastic scattering measurement carried out at the same time
with the transfer measurement. From the transfer, we determined the square of
the ANC, C^2(13Og.s.) = 2.53 +/- 0.30 fm-1, and hence a value of 0.33(4) keVb
was obtained for the direct astrophysical S factor at zero energy. Constructive
interference at low energies between the direct and resonant captures leads to
an enhancement of Stotal(0) = 0.42(5) keVb. The 12N(p,gamma)13O reaction was
investigated in relation to the evolution of hydrogen-rich massive Population
III stars, for the role that it may play in the hot pp-chain nuclear burning
processes, possibly occurring in such objects.Comment: 15 pages, 10 figures, 3 tables submitted to Phys. Rev.
Measurement of the 20 and 90 keV resonances in the N reaction via THM
The reaction is of primary importance in
several astrophysical scenarios, including fluorine nucleosynthesis inside AGB
stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus
the indirect measurement of the low energy region of the reaction has been performed to reduce the nuclear
uncertainty on theoretical predictions. In particular the strength of the 20
and 90 keV resonances have been deduced and the change in the reaction rate
evaluated.Comment: 4 pages, 4 figures, submitted to PR
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