Resonance excitations in the $^{7}$Be + d experiment at CERN ISOLDE

The Big Bang Nucleosynthesis (BBN) theory has been very successful in predicting the observed abundances of light elements like $^2$H, ${3,4}$He. There is, however, a serious discrepancy of a factor of about four in the observed abundance of $^7$Li as compared to that predicted by the BBN theory [1−2]. The high precision measurement of the baryon to photon ratio η by the Wilkinson Microwave Anisotropy Probe (WMAP) and recent observations of metal poor halo stars shows that the $^7$Li abundance predicted by the BBN theory is about $5.12 \times 10^{10}$, whereas the observed value is about $1.23 \times 10^{10}$. This anomaly has been unsolved for decades and is well known. Several avenues have been searched for a solution, of which the resonance excitations in reactions with $^7$Be appear to be very attractive [3].