Cosmological constraints on light but massive relics

Journal Article · Fri May 20 00:00:00 EDT 2022 · Physical Review. D.

DOI:https://doi.org/10.1103/physrevd.105.095029· OSTI ID:1906345

Xu, Weishuang Linda  ^[1]; Muñoz, Julian B.  ^[2]; Dvorkin, Cora ^[1]

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1. Harvard Univ., Cambridge, MA (United States)
2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

Many scenarios of physics beyond the standard model predict new light, weakly coupled degrees of freedom, populated in the early universe and remaining as cosmic relics today. Due to their high abundances, these relics can significantly affect the evolution of the universe. For instance, massless relics produce a shift ΔN_eff to the cosmic expectation of the effective number of active neutrinos. Massive relics, on the other hand, additionally become part of the cosmological dark matter in the later universe, though their light nature allows them to freely stream out of potential wells. This produces novel signatures in the large-scale structure (LSS) of the universe, suppressing matter fluctuations at small scales. Here, we present the first general search for such light (but massive) relics (LiMRs) with cosmic microwave background (CMB) and LSS data, scanning the 2D parameter space of their masses m_X and temperatures $$T^{(0)}_{X}$$ today. In the conservative minimum-temperature ($$T^{(0)}_{X}$$ = 0.91 K) scenario, we rule out Weyl (and higher-spin) fermions -- such as the gravitino -- with m_X ≥ 2.26 eV at 95% C.L., and set analogous limits of m_X ≤ 11.2,1.06,1.56 eV for scalar, vector, and Dirac-fermion relics. This is the first search for LiMRs with joint CMB, weak-lensing, and full-shape galaxy data; we demonstrate that weak-lensing data is critical for breaking parameter degeneracies, while full-shape information presents a significant boost in constraining power relative to analyses with only baryon acoustic oscillation parameters. Under the combined strength of these datasets, our constraints are the tightest and most comprehensive to date.

• Research Organization: Harvard Univ., Cambridge, MA (United States)
• Sponsoring Organization: USDOE; Moore Foundation
• Grant/Contract Number: SC0020223; 8342
• OSTI ID: 1906345
• Journal Information: Physical Review. D., Vol. 105, Issue 9; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS