Seminars IFIC

Ultra-light scalar saving the 3+1 neutrino scheme from the cosmological bounds

by Yasaman Farzan (IPM, Tehran & ICTP, Trieste)

4-4-4426 - Seminari Física Teòrica (Campus Burjassot)

4-4-4426 - Seminari Física Teòrica

Campus Burjassot

The LSND and MiniBooNE results as well as the reactor and Gallium anomalies seem to 
indicate the presence of a sterile neutrino with a mass of ∼1 eV mixed with active 
neutrinos. Such sterile neutrino can be produced in the early universe before the neutrino 
decoupling, leading to a contribution to the effective number of neutrinos (Neff) as well as to a 
contribution to the sum of neutrino masses which are in tension with cosmological 
observations. We propose a scenario to relax this tension by a Yukawa coupling of the sterile 
neutrinos to ultra-light scalar particles which contribute to the dark matter in the 
background. The coupling induces an effective mass for the sterile neutrino which prevents its 
production in the early universe. We discuss the implications for the upcoming KATRIN 
experiment and future relic neutrino search experiments such as PTOLEMY. 
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