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

Théo Simon, Guillermo Franco Abellán+3 more|arXiv (Cornell University)|Mar 14, 2022

Cosmology and Gravitation Theories174 references72 citations

TL;DR

This paper presents the first computation of mildly non-linear galaxy power spectra in decaying dark matter models using the Effective Field Theory of Large-Scale Structures (EFTofLSS) applied to BOSS-DR12 data. It constrains two models—CDM decaying into dark radiation (DR) and CDM decaying into DR plus massive warm dark matter (WDM)—finding that EFTofBOSS data significantly improves constraints on the CDM lifetime, especially when combined with S8 priors from KiDS-1000, favoring longer lifetimes (τ ≈ 120 Gyr) to resolve the S8 tension.

ABSTRACT

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 $f_{ m dcdm}$ of cold dark matter (CDM) decays into dark radiation (DR) with a lifetime $ au$. In the second model (recently suggested as a potential resolution to the $S_8$ tension), all the CDM decays with a lifetime $ au$ into DR and a massive warm dark matter (WDM) particle, with a fraction $\varepsilon$ 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 non-linear (matter and galaxy) power spectra with the EFTofLSS for these two models. In the case of DR products, we obtain the constraints $f_{ m dcdm}\lesssim0.022$ (95\% C.L.) for lifetimes shorter than the age of the universe, and $ au/f_{ m dcdm} \gtrsim 250$ Gyr in the long-lived regime assuming $f_{ m dcdm} o1$. We show that Planck data contributes the most to these constraints, with EFTofBOSS providing a marginal improvement over conventional BAO and redshift space distortions ($f\sigma_8$) 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 $S_8$ prior from KiDS-1000. We show that, in order to fit EFTofBOSS data while lowering $S_8$ to match KiDS-1000, the best-fit model has a longer lifetime $ au = 120$ Gyr, with a larger kick velocity $v_{ m kick}/c \simeq \varepsilon \simeq 1.2\%$, than that without EFTofBOSS ($ au = 43$ Gyr, $\varepsilon =0.6\%$). We anticipate that future surveys will provide exquisite constraints on such models.

Motivation & Objective

• To compute the first mildly non-linear matter and galaxy power spectra in decaying dark matter models using the EFTofLSS formalism.
• To test whether BOSS data analyzed via EFTofLSS improves cosmological constraints on decaying dark matter models compared to conventional BAO and fσ8 data.
• To assess whether decaying dark matter models can resolve the S8 tension, particularly when combined with S8 priors from KiDS-1000.
• To evaluate the role of Planck CMB data and EFTofBOSS in constraining decay parameters such as lifetime τ and fraction fdcdm or energy fraction ε.

Proposed method

• Uses the EFTofLSS formalism to model the full-shape galaxy power spectrum in redshift space, including non-linear corrections via counterterms.
• Applies numerical codes from recent literature to compute the mildly non-linear matter and galaxy power spectra for two DCDM models: CDM → DR and CDM → WDM + DR.
• Performs Markov Chain Monte Carlo (MCMC) analyses using Planck CMB, BOSS-DR12 BAO, fσ8, Pantheon SNIa, and KiDS-1000 S8 data to constrain model parameters.
• Incorporates EFTofLSS data from BOSS to improve constraints on the CDM decay lifetime τ and decay fraction fdcdm or energy transfer fraction ε.
• Uses public codes such as MontePython and CLASS to perform cosmological parameter inference with EFTofLSS corrections.
• Compares results with and without EFTofBOSS to isolate its impact on parameter constraints, particularly for the S8 tension.

Experimental results

Research questions

• RQ1 Can the EFTofLSS formalism improve constraints on decaying dark matter models compared to conventional BAO and fσ8 data?
• RQ2 What are the constraints on the CDM decay lifetime τ and decay fraction fdcdm in the CDM → DR model, especially for lifetimes comparable to or shorter than the age of the universe?
• RQ3 How do constraints on the CDM → WDM + DR model change when EFTofBOSS data is included, particularly in the context of resolving the S8 tension?
• RQ4 Can decaying dark matter models with massive decay products successfully lower σ8 to match the lower S8 value from KiDS-1000, and what decay parameters are favored?
• RQ5 How much does Planck CMB data contribute to the constraints, and what is the marginal improvement from EFTofBOSS?

Key findings

• For the CDM → DR model, the constraint is fdcdm ≲ 0.022 at 95% credible level for lifetimes shorter than the age of the universe.
• In the long-lived regime (fdcdm → 1), the constraint is τ/fdcdm ≳ 250 Gyr, indicating very long CDM lifetimes.
• EFTofBOSS data provides a marginal improvement over conventional BAO and fσ8 data for the CDM → DR model, with Planck CMB dominating the constraints.
• For the CDM → WDM + DR model, EFTofBOSS data significantly improves constraints on the CDM lifetime τ at 68% C.L. when combined with a KiDS-1000 S8 prior.
• To match KiDS-1000’s lower S8 value, the best-fit model requires a longer CDM lifetime τ = 120 Gyr and a larger kick velocity vkick/c ≃ ε ≃ 1.2%, compared to τ = 43 Gyr and ε = 0.6% without EFTofBOSS.
• The study anticipates that future surveys will provide even tighter constraints on decaying dark matter models, especially those addressing the S8 tension.