Measurement of the 10 keV resonance in theB10(p,α0)Be7reaction via the Trojan Horse method

The $^{10}\mathrm{B}(p,{\ensuremath{\alpha}}_{0})^{7}\mathrm{Be}$ bare nucleus astrophysical $S(E)$ factor has been measured for the first time at energies from about 100 keV down to about 5 keV by means of the Trojan Horse method (THM). In this energy region, the $S(E)$ factor is strongly dominated by the 8.699 MeV $^{11}\mathrm{C}$ level (${J}^{\ensuremath{\pi}}={\frac{5}{2}}^{+}$), producing an $s$-wave resonance centered at about 10 keV in the entrance channel. Up to now, only the high--energy tail of this resonance has been measured, while the low-energy trend is extrapolated from the available direct data. The THM has been applied to the quasifree $^{2}\mathrm{H}(^{10}\mathrm{B},{\ensuremath{\alpha}}_{0}$ $^{7}\mathrm{Be}$)n reaction induced at a boron-beam energy of 24.5 MeV. An accurate analysis leads to the determination of the $^{10}\mathrm{B}(p,{\ensuremath{\alpha}}_{0})^{7}\mathrm{Be}$ $S(E)$ factor and of the corresponding electron screening potential ${U}_{e}$, thus giving for the first time an independent evaluation of it.