A direct measurement of the 16O(p,α)13N cross section using the MUSIC active-target detector at energies relevant to type Ia supernovae
Dr. Heshani Jayatissa
Scientist, Intelligence and Space Research (ISR) division
Los Alamos National Laboratory
The 16O(p,α)13N reaction plays an influential role during explosive oxygen burning in Type Ia supernovae by providing an alternative pathway for converting 16O into 12C, and by enhancing the abundance of α particles. This reaction directly impacts the calcium-to-sulphur (Ca/S) production ratio in Type Ia supernovae, a key observable used to probe progenitor metallicity. However, predictions of Ca/S ratios from supernova models show significant discrepancies with observations, partly due to large uncertainties and inconsistencies in the adopted 16O(p,α)13N reaction rates. Existing stellar rate libraries differ by up to an order of magnitude, and it has been suggested that an enhancement of up to seven times the CF88 rate is required to reproduce observed Ca/S trends. A critical evaluation of available experimental cross-section data reveals substantial discrepancies in the low-energy region (Ecm ≈ 5.7–7.0 MeV), largely arising from limitations of previous activation measurements. To address this, a new measurement of the 16O(p,α)13N reaction has been performed in inverse kinematics using the MUSIC active-target detector, enabling direct detection of (p,α) events for the first time. The resulting data provide a more reliable experimental constraint on the cross section and were used to derive an updated thermonuclear reaction rate.
Hosted by Prof. Couder
Zoom link: https://notredame.zoom.us/j/99165675577.