| Přispěvatelé: |
Ferraro, F., Takács, M. P., Piatti, D., Cavanna, F., Depalo, R., Aliotta, M., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Chillery, T., Ciani, G. F., Corvisiero, P., Davinson, T., D'Erasmo, G., Di Leva, A., Elekes, Z., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Karakas, A., Kochanek, I., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F. R., Paticchio, V., Perrino, R., Prati, P., Schiavulli, L., Stöckel, K., Straniero, O., Szücs, T., Trezzi, D., Zavatarelli, S. |
| Popis: |
The ^{22}Ne(p,γ)^{23}Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E_{p}=156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E_{p}=71 and 105 keV. Here, new ^{22}Ne(p,γ)^{23}Na data with high statistics and low background are reported. Stringent upper limits of 6×10^{-11} and 7×10^{-11} eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the ^{22}Ne(p,γ)^{23}Na rate is now reduced by 3 orders of magnitude. |
