Revisiting Lithium-7 Constraints with a Light Decoupled Dark Sector

We investigate a light, decoupled dark sector that could modify Big-Bang Nucleosynthesis and potentially reduce the primordial Li7 abundance. In this framework, a dark particle freezes out from the dark-sector thermal bath and subsequently injects energy into the visible sector, influencing the expansion rate and temperature evolution during nucleosynthesis. To explore this possibility, we are developing a custom thermodynamic treatment coupled to public BBN solvers. Our ongoing scans over the dark-sector parameter space aim to determine whether regions exist that can alleviate the lithium problem while remaining consistent with deuterium and helium observations. Although the viability of this scenario is still under examination, the mechanism provides a well-motivated direction for understanding potential cosmological signatures of hidden thermal sectors.