Cosmological constraints on invisible neutrino decays revisited

Abstract

Neutrinos could decay. Invisible neutrino decay modes are difficult to target at laboratory experiments, and current bounds on such decays from solar neutrino and neutrino oscillation experiments are somewhat weak. It has been known for some time that Cosmology can serve as a powerful probe of invisible neutrino decays. In this work, we show that in order for Big Bang Nucleosynthesis to be successful, the invisible neutrino decay lifetime should be τν > 10 −3 s. We revisit Cosmic Microwave Background constraints on invisible neutrino decays, and by using the latest Planck observations we find that neutrino lifetimes τν < (1.2 − 0.3) × 10 9 s (mν /0.05 eV) 3 are excluded at 95% CL. We show that this bound is robust to modifications of the cosmological model, in particular that it is independent of the presence of dark radiation. We find that typical invisible neutrino decay modes with rates τν < 10 5 s (mν /0.05 eV) 3 are disfavoured at more than 5 σ with respect to ΛCDM given the latest Planck CMB observations. Finally, we show that when including high-Planck polarization data, neutrino lifetimes τν = (2 − 14) × 10 9 s (mν /0.05 eV) 3 are mildly preferred -with a 1-2 σ significance -over neutrinos being stable.

Intramolecular BSSE and dispersion affect the structure of a dipeptide conformer

“…n/a n/a n/a 137.4 6.08 B3LYP/cc-pVDZ n/a n/a n/a 138.0 7.24 B3LYP/cc-pVTZ n/a n/a n/a 136.8 7.33 B3LYP/cc-pVQZ n/a n/a n/a 137. [70][71][72], there is recognition that BSSE may be sufficiently large in DFT calculations to warrant correction [16,73,74]. Our results support this.…”

A CMB search for the neutrino mass mechanism and its relation to the Hubble tension

“…where the first term in the denominator results from the majoron production by inverse neutrino decays and the second term (i.e. λ < 4 × 10 −5 ) arises from the production of majorons via neutrino-neutrino annihilations (see [33]). Primordial Majoron Abundance: Majoron interactions with the Standard Model arise through the active-sterile neutrino mixing [12], implying that majorons have non-negligible interactions with heavy sterile neutrinos.…”

Cosmological limits on the neutrino mass and lifetime

“…If neutrino decay and inverse decay processes are effective during the CMB epoch, they prevent the neutrinos from free streaming, leading to observable effects on the CMB [42][43][44]. Current measurements of the CMB power spectra require neutrinos to JHEP04(2020)020 free stream from redshifts z ≈ 8000 until recombination, z ≈ 1100 [45][46][47][48]. 1 This can be used to set a lower bound on the neutrino lifetime τ ν ≥ 4 × 10 8 s (m ν /0.05 eV) 3 for SM neutrinos decaying into massless dark radiation [48].…”

“…Current measurements of the CMB power spectra require neutrinos to JHEP04(2020)020 free stream from redshifts z ≈ 8000 until recombination, z ≈ 1100 [45][46][47][48]. 1 This can be used to set a lower bound on the neutrino lifetime τ ν ≥ 4 × 10 8 s (m ν /0.05 eV) 3 for SM neutrinos decaying into massless dark radiation [48]. Several astrophysical observations have also been used to set limits on the neutrino lifetime.…”