C. Tur

PRODUCTION OF 26Al, 44Ti, AND 60Fe IN CORE-COLLAPSE SUPERNOVAE: SENSITIVITY TO THE RATES OF THE TRIPLE ALPHA AND 12C(α, γ)16O REACTIONS

We have studied the sensitivity to variations in the triple alpha and 12C(?, ?)16O reaction rates of the production of 26Al, 44Ti, and 60Fe in core-collapse supernovae (SNe). We used the KEPLER code to model the evolution of 15 M ?, 20 M ?, and 25 M ? stars to the onset of core collapse and simulated the ensuing SN explosion using a piston model for the explosion and an explosion energy of 1.2 ? 1051 erg. Calculations were performed for the Anders & Grevesse and Lodders abundances. Over a range of twice the experimental uncertainty, ?, for each helium-burning rate, the production of 26Al, 60Fe, and their ratio vary by factors of 5 or more. For some species, similar variations were observed for much smaller rate changes, 0.5? or less. The production of 44Ti was less sensitive to changes in the helium-burning rates. Production of all three isotopes depended on the solar abundance set used for the initial stellar composition.

ON THE SENSITIVITY OF MASSIVE STAR NUCLEOSYNTHESIS AND EVOLUTION TO SOLAR ABUNDANCES AND TO UNCERTAINTIES IN HELIUM-BURNING REACTION RATES

We explore the dependence of presupernova evolution and supernova nucleosynthesis yields on the uncertainties in helium-burning reaction rates. Using the revised solar abundances of Lodders for the initial stellar composition, instead of those of Anders and Grevesse, changes the supernova yields and limits the constraints that those yields place on the 12C(α,γ)16O reaction rate. The production factors of medium-weight elements (A = 16-40) were found to be in reasonable agreement with observed solar ratios within the current experimental uncertainties in the triple-α reaction rate. Simultaneous variations by the same amount in both reaction rates or in either of them separately, however, can induce significant changes in the central 12C abundance at core carbon ignition and in the mass of the supernova remnant. It therefore remains important to have experimental determinations of the helium-burning rates so that their ratio and absolute values are known with an accuracy of 10% or better.

Dependence of s-Process Nucleosynthesis in Massive Stars on Triple-Alpha and 12C(α, γ)16O Reaction Rate Uncertainties

We have studied the sensitivity of s-process nucleosynthesis in massive stars to ±2σ variations in the rates of the triple-α and 12C(α, γ)16O reactions. We simulated the evolution of massive stars from H burning through Fe-core collapse, followed by a supernova explosion. We found that the production factors of s-process nuclides between 58Fe and 96Zr change strongly with changes in the He burning reaction rates; using the Lodders solar abundances rather than those of Anders and Grevesse reduces s-process nucleosynthesis; later burning phases beyond core He burning and shell C burning have a significant effect on post-explosive production factors. We also discuss the implications of the uncertainties in the helium burning rates for evidence of a new primary neutron capture process (LEPP) in massive stars.

The (150)Nd((3)He,t) and (150)Sm(t,(3)He) reactions with applications to beta beta decay of (150)Nd

The

B 11 and Constraints on Neutrino Oscillations and Spectra from Neutrino Nucleosynthesis

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Gamow-Teller transitions to Cu 64 measured with the Zn 64 ( t , He 3 ) reaction

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Gamow-Teller transitions to 64-Cu measured using the 64-Zn(t,3-He) reaction

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Gamow-Teller transitions toCu64measured with theZn64(t,He3) reaction

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34P(7Li,7Be+γ) reaction at 100A MeV in inverse kinematics.

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Gamow-Teller unit cross sections for (t,He3) and (He3,t) reactions

) reaction at 140 MeV/u and