Possible solution to the $^7$Li problem by the long lived stau

Understand

Modification of standard big-bang nucleosynthesis is considered in the minimal supersymmetric standard model to resolve the excessive theoretical prediction of the abundance of primordial lithium 7.

• We focus on the stau as a next-lightest superparticle, which is long lived due to its small mass difference with the lightest superparticle.
• It provides a number of additional decay processes of $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$.
• A particularly important process is the internal conversion in the stau-nucleus bound state, which destroys the $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$ effectively.