Journal
PHYSICAL REVIEW D
Volume 105, Issue 6, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevD.105.063525
Keywords
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Funding
- CNRS-IN2P3 Grant Dark21
- ANR [ANR-18-CE31-0006]
- national CNRS-INSU program PNHE
- national CNRS-INSU program PNCG
- European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie Grant [690575, 674896, 860881-HIDDeN]
- OCEVU Labex [ANR-11-LABX-0060]
- Excellence Initiative of Aix-Marseille University (A*MIDEX) of the Investissements d'Avenir programme
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Recent surveys have found a significant discrepancy between the direct measurement of the parameter combination S-8 and the value inferred from cosmic microwave background data. This article proposes that the tension can be resolved if dark matter decays into massless and massive particles and transfers a fraction of its energy to the massless component. The proposed scenario is consistent with various astronomical observations.
Recent weak-lensing surveys have revealed that the direct measurement of the parameter combination S-8 equivalent to sigma(8)(Omega(m)/0.3)(0.5)-where sigma(8) is a measure of the amplitude of matter fluctuations on 8 h(-1) Mpc scales-is similar to 3 sigma discrepant with the value reconstructed from cosmic microwave background (CMB) data assuming the Lambda-cold dark matter (Lambda CDM) model. In this article, we show that it is possible to resolve the tension if dark matter (DM) decays with a lifetime of Gamma(-1) similar or equal to 55 Gyrs into one massless and one massive product, and transfers a fraction epsilon similar or equal to 0.7% of its rest mass energy to the massless component. The velocity kick received by the massive daughter leads to a suppression of gravitational clustering below its free-streaming length, thereby reducing the sigma(8) value as compared to that inferred from the standard Lambda CDM model, in a similar fashion to massive neutrino and standard warm DM. Contrarily to the latter scenarios, the time dependence of the power suppression and the free-streaming scale allows the 2-body decaying DM scenario to accommodate CMB, baryon acoustic oscillation, growth factor and uncalibrated supernova Ia data. We briefly discuss implications for DM model building, galactic small-scale structure problems and the recent Xenon-1T excess. Future experiments measuring the growth factor to high accuracy at 0 less than or similar to z less than or similar to 1 can further test this scenario.
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