Strongest model-independent bound on the lifetime of Dark Matter

Audren, Benjamin; Tram, Thomas; Mangano, Gianpiero; Lesgourgues, Julien; Serpico, Pasquale Dario

doi:10.1088/1475-7516/2014/12/028

Article
Report number	arXiv:1407.2418 ; CERN-PH-TH-2014-105
Title	Strongest model-independent bound on the lifetime of Dark Matter
Author(s)	Audren, Benjamin (ITPP, Lausanne) ; Lesgourgues, Julien (ITPP, Lausanne ; CERN ; Annecy, LAPTH) ; Mangano, Gianpiero (INFN, Naples) ; Serpico, Pasquale Dario (Annecy, LAPTH) ; Tram, Thomas (ITPP, Lausanne)
Publication	2014
Imprint	09 Jul 2014
Number of pages	15
Note	Comments: 15 pages, 5 figures. Prepared for submission to JCAP
In:	JCAP 12 (2014) 028
DOI	10.1088/1475-7516/2014/12/028
Subject category	Astrophysics and Astronomy
Abstract	Dark Matter is essential for structure formation in the late Universe so it must be stable on cosmological time scales. But how stable exactly? Only assuming decays into relativistic particles, we report an otherwise model independent bound on the lifetime of Dark Matter using current cosmological data. Since these decays affect only the low-$\ell$ multipoles of the CMB, the Dark Matter lifetime is expected to correlate with the tensor-to-scalar ratio $r$ as well as curvature $\Omega_k$. We consider two models, including $r$ and $r+\Omega_k$ respectively, versus data from Planck, WMAP, WiggleZ and Baryon Acoustic Oscillations, with or without the BICEP2 data (if interpreted in terms of primordial gravitational waves). This results in a lower bound on the lifetime of CDM given by 160Gyr (without BICEP2) or 200Gyr (with BICEP2) at 95% confidence level.
Copyright/License	Preprint: © 2014-2025 CERN (License: CC-BY-3.0)

$CMB temperature power spectrum for a variety of models, all with the same parameters $\{100\,\theta_s, \omega_\mathrm{dcdm}^\mathrm{ini}, \omega_\mathrm{b}, \ln(10^{10} A_s), n_s, \tau_\mathrm{reio} \} = \{1.04119, 0.12038, 0.022032, 3.0980, 0.9619, 0.0925\}$ taken from the Planck+WP best fit~\cite{Ade:2013zuv}. For all models except the ``Decaying CDM'' one, the decay rate $\Gamma_\mathrm{dcdm}$ is set to zero, implying that the ``dcdm'' species is equivalent to standard cold DM with a present density $\omega_\mathrm{cdm} = \omega_\mathrm{dcdm}^\mathrm{ini} = 0.12038$. The ``Decaying CDM'' model has $\Gamma_\mathrm{dcdm}=20\,\mbox{km s}^{-1}\mbox{Mpc}^{-1}$, the ``Tensors'' model has $r=0.2$, and the ``Open'' (``Closed'') models have $\Omega_k = 0.02$ ($-0.2$). The main differences occur at low multiples and comes from either different late ISW contributions or non-zero tensor fluctuations.$ $The single contributions to the CMB temperature spectrum (Sachs-Wolfe, early and late Integrated Sachs-Wolfe, Doppler and polarisation-induced) for a stable model (solid) and a dcdm model (dashed) with $\Gamma_\mathrm{dcdm}=100$~km/s/Mpc. The value of other parameters is set as in Figure~\ref{fig:cltot}. We see that only the late ISW effect is sensitive to the decay rate (for other contributions, solid and dashed lines are indistinguishable).$ $Matter power spectrum $P(k)$ (computed in the Newtonian gauge) for the same models considered in Figure~\ref{fig:cltot}. The black curve (Stable CDM) is hidden behind the red one (Tensors).$ Show more plots

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