Direct measurement of the Li 7 ( p , α ) He 4 reaction at astrophysical energies using the ELISSA array

A direct measurement of the Li 7 ( p , α ) He 4 reaction at astrophysical energies was performed at the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) using a scaled-down version of the ELISSA detector array and the 3 MV Tandem accelerator. This reaction plays a crucial role in both primordial and stellar nucleosynthesis. In Big-Bang Nucleosynthesis (BBN), it is directly linked to the long-standing “Cosmological Lithium Problem,” the discrepancy between observed and predicted primordial Li 7 abundances. In stellar environments, it constitutes the final step in the hydrogen-to-helium burning chain. The experiment utilized a Li 7 beam incident on a CH 2 target at ten laboratory energies ( E lab ) corresponding to center-of-mass energies ( E c.m. ) ranging from 59.5 to 990 keV. The astrophysical S factors were extracted using both the Distorted Wave Born Approximation (DWBA) and polynomial fitting techniques. Updated reaction rates were calculated from the present DWBA results, supplemented by existing experimental data. The impact of the theoretical DWBA calculation on the reaction rate is investigated.