Was entropy conserved between BBN and recombination?

We test the assumption of entropy conservation between Big Bang nucleosynthesis and recombination by considering a massive particle that decays into mixture photons other relativistic species. employ Planck temperature polarization anisotropies, COBE/FIRAS spectral distortion bounds, observed primordial deuterium abundance to constrain these decay scenarios. If $56\%$ $71\%$ decaying particle's energy is transferred photons, then $N_{\mathrm{eff}}$ at minimally altered, data alone allows for significant injection. are injected decay, addition bounds restricts rate be $\Gamma_Y > 1.91\times10^{-6} \text{s}^{-1}$ $95\%$ confidence level (C.L.). find constraints on density significantly enhanced inclusion abundance, allowing contribute most $2.35\%$ ($95\%$ C.L.) universe before decaying.