DCDM Constraints Summary
This note studies decaying cold dark matter (DCDM) with invisible decay into dark radiation using Planck 2018 TT,TE,EE+lowE+lensing likelihoods.
Method
A profile-likelihood approach is used: for fixed decay rates, remaining cosmological parameters are re-optimized to extract robust one-sided upper bounds.
Main result
No evidence for dark-matter decay is found in the sampled range. The 95% confidence upper bound is Γdcdm ≲ 2.4 km s−1 Mpc−1, corresponding to a lifetime τdcdm ≳ 4 × 1011 years.
Interpretation
Within this model and data combination, the stable-CDM limit remains the global best-fit scenario.