@bdasgupta

Viable secret neutrino interactions with ultralight dark matter

. (2019)cite arxiv:1908.02278Comment: 5 pages, 1 figure; submitted to PLB (not PRL).

Abstract

Several anomalies in neutrino oscillation experiments point to the existence of a $1\,$eV sterile neutrino $\nu_s$ mixing with $\nu_e$ at the level of $U_e40.1$, but such a neutrino is strongly disfavored by constraints on additional light degrees of freedom ($N_eff$) and total neutrino mass ($\sum_m_\nu$) from cosmology. ``Secret neutrino interactions'' that have been invoked to suppress the cosmological production of $\nu_s$ typically falter, but recently it was pointed out that $\nu_s$ could get a large mass in the early universe by coupling to ultralight dark matter $\phi$, which can robustly suppress its production. The model has essentially two free parameters: $m_\phi$, and $m_s,0$, the mass of the sterile neutrino at early times, enhanced by its coupling to $\phi$. I determine the parameter regions allowed by limits on $N_eff$ and $\sum_m_\nu$ from the cosmic microwave background and big bang nucleosynthesis, using a simplified yet accurate treatment of neutrino oscillations in the early universe. This mechanism could have an important impact on laboratory experiments that suggest oscillations with sterile neutrinos.

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Viable secret neutrino interactions with ultralight dark matter

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