First measurement of the low-energy direct capture in ²⁰Ne(p,γ)²¹Na and improved energy and strength of the E(c.m.) = 368 keV resonance

First measurement of the low-energy direct capture in ²⁰Ne(p,γ)²¹Na and improved energy and strength of the E(c.m.) = 368 keV resonance

Masha, E.; Barbieri, L.; Skowronski, J.; Aliotta, M.; Ananna, C.; Barile, F.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Campostrini, M.; Casaburo, F.; Cavanna, F.; Ciani, G. F.; Ciapponi, A.; Colombetti, P.; Compagnucci, A.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; José, J.; Junker, M.; Lugaro, M.; Manoj, P.; Marigo, P.; Menegazzo, R.; Paticchio, V.; Piatti, D.; Prati, P.; Rapagnani, D.; Rigato, V.; Robb, D.; Schiavulli, L.; Sidhu, R. S.; Straniero, O.; Szücs, T.; Zavatarelli, S.

The ²⁰Ne(p,γ)²¹Na reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below E(c.m.) = 352 keV, and of the contribution from the E(c.m.) = 368 keV resonance, which dominates the reaction rate at T = 0.03–1.00 GK. The experiment was performed deep underground at the Laboratory for Underground Nuclear Astrophysics, using a high-intensity proton beam and a windowless neon gas target. Prompt γ rays from the reaction were detected with two high-purity germanium detectors. We obtain a resonance strength ωγ = (0.112 ± 0.002(stat) ± 0.005(sys)) meV, with an uncertainty a factor of 3 smaller than previous values. Our revised reaction rate is 20% lower than previously adopted at T < 0.1 GK and agrees with previous estimates at temperatures T ≤ 0.1 GK. Initial astrophysical implications are presented.

Keywords: Nuclear Astrophysics; Underground Laboratory; Cross Section Measurement; Neon-Sodium-Cycle; LUNA

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