Constraining decaying dark matter with BOSS data and the effective field theory of large-scale structures

We update cosmological constraints on two decaying dark matter models in light of BOSS-DR12 data analyzed under the effective field theory of large-scale structures (EFTofLSS) formalism, together with Planck, Pantheon and other BOSS measurements of the baryonic acoustic oscillation (BAO). In the first model, a fraction fdcdm of cold dark matter (CDM) decays into dark radiation (DR) with a lifetime τ . In the second model (recently suggested as a potential resolution to the S8 tension), all the CDM decays with a lifetime τ into DR and a massive warm dark matter (WDM) particle, with a fraction ϵ of the CDM rest mass energy transferred to the DR. Using numerical codes from the recent literature, we perform the first calculation of the mildly nonlinear (matter and galaxy) power spectra with the EFTofLSS for these two models. In the case of DR products, we obtain the constraints fdcdm≲0.022 (95% C.L.) for lifetimes shorter than the age of the Universe, and τ/fdcdm≳250 Gyr in the long-lived regime assuming fdcdm → 1 . We show that Planck data contributes the most to these constraints, with EFTofBOSS providing a marginal improvement over conventional BAO and redshift space distortions ( fσ8 ) data. In the case of DR and WDM decay products, we find that EFTofBOSS data significantly improves the constraints at 68% C.L. on the CDM lifetime with a S8 prior from KiDS-1000. We show that, in order to fit EFTofBOSS data while lowering S8 to match KiDS-1000, the best-fit model has a longer lifetime τ=120 Gyr , with a larger kick velocity vkick/c≃ϵ≃1.2% , than that without EFTofBOSS ( τ=43 Gyr , ϵ=0.6% ). We anticipate that future surveys will provide exquisite constraints on such models.