14 research outputs found
Angular Dependence in Proton-Proton Correlation Functions in Central and Reactions
The angular dependence of proton-proton correlation functions is studied in
central and nuclear reactions at E=80
MeV/A. Measurements were performed with the HiRA detector complemented by the
4 Array at NSCL. A striking angular dependence in the laboratory frame is
found within p-p correlation functions for both systems that greatly exceeds
the measured and expected isospin dependent difference between the neutron-rich
and neutron-deficient systems. Sources measured at backward angles reflect the
participant zone of the reaction, while much larger sources observed at forward
angles reflect the expanding, fragmenting and evaporating projectile remnants.
The decrease of the size of the source with increasing momentum is observed at
backward angles while a weaker trend in the opposite direction is observed at
forward angles. The results are compared to the theoretical calculations using
the BUU transport model.Comment: 8 pages, 3 figures, submitted to PR
Constraining nova observables: direct measurements of resonance strengths in 33S(p,\gamma)34Cl
The 33S(p,\gamma)34Cl reaction is important for constraining predictions of
certain isotopic abundances in oxygen-neon novae. Models currently predict as
much as 150 times the solar abundance of 33S in oxygen-neon nova ejecta. This
overproduction factor may, however, vary by orders of magnitude due to
uncertainties in the 33S(p,\gamma)34Cl reaction rate at nova peak temperatures.
Depending on this rate, 33S could potentially be used as a diagnostic tool for
classifying certain types of presolar grains. Better knowledge of the
33S(p,\gamma)34Cl rate would also aid in interpreting nova observations over
the S-Ca mass region and contribute to the firm establishment of the maximum
endpoint of nova nucleosynthesis. Additionally, the total S elemental abundance
which is affected by this reaction has been proposed as a thermometer to study
the peak temperatures of novae. Previously, the 33S(p,\gamma)34Cl reaction rate
had only been studied directly down to resonance energies of 432 keV. However,
for nova peak temperatures of 0.2-0.4 GK there are 7 known states in 34Cl both
below the 432 keV resonance and within the Gamow window that could play a
dominant role. Direct measurements of the resonance strengths of these states
were performed using the DRAGON recoil separator at TRIUMF. Additionally two
new states within this energy region are reported. Several hydrodynamic
simulations have been performed, using all available experimental information
for the 33S(p,\gamma)34Cl rate, to explore the impact of the remaining
uncertainty in this rate on nucleosynthesis in nova explosions. These
calculations give a range of ~ 20-150 for the expected 33S overproduction
factor, and a range of ~ 100-450 for the 32S/33S ratio expected in ONe novae.Comment: 12 pages, 8 figures, Accepted for publication in Physical Review
Reading and writing: Narrative motifs of sexual and epistemic violence in Waiting for the Barbarians
Isospin effects in 40,48Ca+40,48Ca collisions
Expérience à MSU-NSCLInternational audienceThe isospin dependence of two proton correlations is studied in 40Ca+40Ca and 48Ca+48Ca collisions at E/A = 80 MeV. Measurements were performed with the HiRA detector array complemented by the 4π Ball at NSCL. We observe a strong isospin dependence of the ppcorrelation functions; however the emitting source radius extracted using the imaging technique yields no sensitivity to the isospin of the reaction system. We interpret this result as a consequence of smaller fraction of fast proton emission in the neutron rich 48Ca system