The Strong and Weak Lithium Anomaly in BBN

The measured abundance for $^{7}$Li is within a factor of two agreement with the standard Big Bang Nucleosynthesis (BBN) models, however for the more fragile $^{6}$Li, its abundance has been observed at a level three orders of magnitude above those predicted by standard BBN model. These discrepancies are known as the \textit{Lithium Anomaly}. The standard BBN model predicts an abundance ratio for [$^{7}$Li / $^{6}$Li] on the order of a 1000 or greater. Precise measurements of isotopic ratio indicate that [$^{7}$Li / $^{6}$Li] $\approx $ 12.3. This discrepancy is the \textit{Strong Lithium Anomaly}. The measured abundance [$^{7}$Li / $^{1}$H] $\approx $ (1.5 \underline {+} 0.3) x 10$^{-10 }$is a factor of two lower than the abundance [$^{7}$Li/$^{1}$H] $\approx $ (3.82 \underline {+} 0.70) x 10$^{-10 }$predicted by the standard BBN calculations, and this discrepancy is the \textit{Weak Lithium Anomaly}. A quick review will be done of the reactions that have been included in the BBN calculations of Lithium-6 abundance. I will discuss an experiment to address the \textit{Lithium Anomaly}, via the $^{7}$Li($^{3}$He, $^{4}$He)$^{6}$Li reaction using the TACTIC detector at TRIUMF.