Cl β-delayed proton decay and its effect on ONe nova nucleosynthesis*

The ³⁰P(p,γ)³¹S reaction rate plays a crucial role in understanding the nucleosynthesis of oxygen-neon (ONe) novae.  This thermonuclear rate influences the isotopic and chemical abundances of nova ejecta, and constraing this reaction rate could help identify candidate presolar nova grains as well as provide more accurate calibrations for nova thermometers. The reaction proceeds primarily via proton capture into narrow, isolated resonance states lying just above the proton-separation energy in ³¹S. By determining the strength of a recently observed low-energy, J^π = 3/2⁺ resonance, we can substantially reduce the nuclear uncertainties associated with modeling explosive nucleosynthesis in novae. Here we report the results of a ³¹Cl β-delayed proton decay experiment in which we meausred the very weak proton decay branch of this potentially dominant resonance. This represents the weakest β+-delayed particle emission ever measured for resonances below 400 keV. Using our experimentally determined proton branching ratio as well as available information in literature, we calculated the new total thermonuclear rate for ³⁰P(p,γ)³¹S and interpret its astrophysical impact with fully hydrodynamic 1D nova simulations.