Measurement of the 2H(7Be, 6Li)3He reaction rate and its contribution to the primordial lithium abundance

In the standard Big Bang nucleosynthesis (SBBN) model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered. ⁷Be(d, ³He)⁶Li is a reaction that not only produces ⁶Li but also destroys ⁷Be, which decays to ⁷Li, thereby affecting ⁷Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high. However, there is not much information available about the ⁷Be(d, ³He)⁶Li reaction rate. In this work, the angular distributions of the ⁷Be(d, ³He)⁶Li reaction are measured at the center of mass energies E _cm = 4.0 MeV and 6.7 MeV with secondary ⁷Be beams for the first time. The excitation function of the ⁷Be(d, ³He)⁶Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the ⁶Li and ⁷Li abundances. The results show that the ⁷Be(d, ³He)⁶Li reaction has a minimal effect on ⁶Li and ⁷Li because of its small reaction rate. Therefore, the ⁷Be(d, ³He)⁶Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.

Supported by National Natural Science Foundation of China (11375269, 11505117, 11490560, 11475264, 11321064), Natural Science Foundation of Guangdong Province (2015A030310012), 973 program of China (2013CB834406) and National key Research and Development Province (2016YFA0400502)