Indirect study of 11B(p,0)8Be and 10B(p,)7Be reactions at astrophysical energies by means of the Trojan Horse Method: recent results

摘要

Nuclear (p) reactions destroying the so-called “light-elements” lithium, beryllium and boron have been largely studied in the past mainly because their role in understanding some astrophysical phenomena, i.e. mixing-phenomena occurring in young F-G stars [1]. Such mechanisms transport the surface material down to the region close to the nuclear destruction zone, where typical temperatures of the order of 106 K are reached. The corresponding Gamow energy E0=1.22(Z2 xZ2 XT2 6) 1 3 keV [2] is about 10 keV if one considers the “boron-case” and replaces in the previous formula Zx = 1, ZX = 5 and T6=5.Direct measurements of the two 11B(p,0)8Be and 10B(p,)7Be reactions in correspondence of this energy region are difficult to perform mainly because the combined effects of Coulomb barrier penetrability and electron screening [3]. The indirect method of the Trojan Horse (THM) [4–6] allows one to extract the two-body reaction cross section of interest for astrophysics without the extrapolation-procedures. Due to the THM formalism, the extracted indirect data have to be normalized to the available direct ones at higher energies thus implying that the method is a complementary tool in solving some still open questions for both nuclear and astrophysical issues [7–12].