TY  - JOUR
AU  - Barenboim, G.
AU  - Chen, J. Z.
AU  - Hannestad, S.
AU  - Oldengott, I. M.
AU  - Tram, T.
AU  - Wong, Y. Y. Y.
PY  - 2021
DA  - 2021//
TI  - Invisible neutrino decay in precision cosmology
T2  - J. Cosmol. Astropart. Phys.
JO  - Journal of Cosmology and Astroparticle Physics
SP  - 087
EP  - 53pp
VL  - 03
IS  - 3
PB  - Iop Publishing Ltd
KW  - cosmological neutrinos
KW  - neutrino properties
KW  - CMBR theory
KW  - cosmological parameters from CMBR
AB  - We revisit the topic of invisible neutrino decay in the precision cosmological context, via a first-principles approach to understanding the cosmic microwave background and large-scale structure phenomenology of such a non-standard physics scenario. Assuming an effective Lagrangian in which a heavier standard-model neutrino nu(H) couples to a lighter one nu(l) and a massless scalar particle phi via a Yukawa interaction, we derive from first principles the complete set of Boltzmann equations, at both the spatially homogeneous and the firstorder inhomogeneous levels, for the phase space densities of nu(H), nu(l), and phi in the presence of the relevant decay and inverse decay processes. With this set of equations in hand, we perform a critical survey of recent works on cosmological invisible neutrino decay in both limits of decay while nu(H) is ultra-relativistic and non-relativistic. Our two main findings are: (i) in the non-relativistic limit, the effective equations of motion used to describe perturbations in the neutrino-scalar system in the existing literature formally violate momentum conservation and gauge invariance, and (ii) in the ultra-relativistic limit, exponential damping of the anisotropic stress does not occur at the commonly-used rate Gamma(T) = (1/tau(0))( m(nu H)/E-nu H)(3), but at a rate similar to (1/ tau(0))(m(nu H)/E-nu H)(5). Both results are model-independent. The impact of the former finding on the cosmology of invisible neutrino decay is likely small. The latter, however, implies a significant revision of the cosmological limit on the neutrino lifetime tau(0) from tau(old)(0) greater than or similar to 1.2 x 10(9) s (m(nu H)/50 meV)(3) to tau(0) greater than or similar to (4 x 10(5) -> 4 x 10(6)) s (m(nu H)/50 meV)(5).
SN  - 1475-7516
UR  - https://arxiv.org/abs/2011.01502
UR  - https://doi.org/10.1088/1475-7516/2021/03/087
DO  - 10.1088/1475-7516/2021/03/087
LA  - English
N1  - WOS:000636717400082
ID  - Barenboim_etal2021
ER  -