Help Privacy Policy Disclaimer
  Advanced SearchBrowse




Journal Article

Dirac neutrinos and Neff II: the freeze-in case


Rodejohann,  Werner
Werner Rodejohann - ERC Starting Grant, Junior Research Groups, MPI for Nuclear Physics, Max Planck Society;


Xu,  Xunjie
Division Prof. Dr. Manfred Lindner, MPI for Nuclear Physics, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)

(Preprint), 2MB

Supplementary Material (public)
There is no public supplementary material available

Luo, X., Rodejohann, W., & Xu, X. (2021). Dirac neutrinos and Neff II: the freeze-in case. Journal of Cosmology and Astroparticle Physics, 2021: 082. doi:10.1088/1475-7516/2021/03/082.

Cite as: https://hdl.handle.net/21.11116/0000-0009-032C-3
We discuss Dirac neutrinos whose right-handed component $\nu_R$ has new
interactions that may lead to a measurable contribution to the effective number
of relativistic neutrino species $N_{\rm eff}$. We aim at a model-independent
and comprehensive study on a variety of possibilities. Processes for
$\nu_R$-genesis from decay or scattering of thermal species, with spin-0,
spin-1/2, or spin-1 initial or final states are all covered. We calculate
numerically and analytically the contribution of $\nu_R$ to $N_{\rm eff}$
primarily in the freeze-in regime, since the freeze-out regime has been studied
before. While our approximate analytical results apply only to freeze-in, our
numerical calculations work for freeze-out as well, including the transition
between the two regimes. Using current and future constraints on $N_{\rm eff}$,
we obtain limits and sensitivities of CMB experiments on masses and couplings
of the new interactions. As a by-product, we obtain the contribution of
Higgs-neutrino interactions, $\Delta N_{\rm eff}^{\rm SM} \approx
7.5\times10^{-12}$, assuming the neutrino mass is 0.1 eV and generated by the
standard Higgs mechanism.