Search for new resonant states in 10C and 11C and their impact on the cosmological lithium problem

The observed primordial ⁷Li abundance in metal-poor halo stars is found to be lower than its Big-Bang nucleosynthesis (BBN) calculated value by a factor of approximately three. Some recent works suggested the possibility that this discrepancy originates from missing resonant reactions which would destroy ⁷Be, parent of ⁷Li. The most promising candidate resonances which were found include a possibly missed 1^- or 2^- narrow state around 15 MeV in the compound nucleus ¹⁰C formed by ⁷Be+³He and a state close to 7.8 MeV in the compound nucleus ¹¹C formed by ⁷Be+⁴He. In this work, we studied the high excitation energy region of ¹⁰C and the low excitation energy region in ¹¹C via the reactions ¹⁰B(³He,t)¹⁰C and ¹¹B(³He,t)¹¹C, respectively, at the incident energy of 35 MeV. Our results for ¹⁰C do not support ⁷Be+³He as a possible solution for the ⁷Li problem. Concerning ¹¹C results, the data show no new resonances in the excitation energy region of interest and this excludes the ⁷Be+⁴He reaction channel as an explanation for the ⁷Li deficit.