Abstract
A number of experimental anomalies involving neutrinos hint towards the existence of at least an extra (a very light) sterile neutrino. However, such a species, appreciably mixing with the active neutrinos, is disfavored by different cosmological observations like Big Bang Nucleosynthesis (BBN), Cosmic Microwave Background (CMB) and Large Scale Structure (LSS). Recently, it was shown that the presence of additional interactions in the sterile neutrino sector via light bosonic mediators can make the scenario cosmologically viable by suppressing the production of the sterile neutrinos from active neutrinos via matter-like effect caused by the mediator. This mechanism works assuming the initial population of this sterile sector to be negligible with respect to that of the Standard Model (SM) particles, before the production from active neutrinos. However, there is fair chance that such bosonic mediators may couple to the inflaton and can be copiously produced during (p)reheating epoch. Consequently, they may ruin this assumption of initial small density of the sterile sector. In this article we, starting from inflation, investigate the production of such a sterile sector during (p)reheating in a large field inflationary scenario and identify the parameter region that allows for a viable early Universe cosmology.
Highlights
There are significant tension among different neutrino experiments
In this article we investigated for the possibility of having an extra sterile neutrino in the particle spectrum
It is wellknown that it is possible to reconcile the cosmological observations with this extra species, if we introduce a pseudoscalar interacting with the sterile neutrinos
Summary
There are significant tension among different neutrino experiments. In particular, observed excess in the experiments measuring νμ(νμ) → νe(νe) appearance (i.e. LSND and MiniBooNE) are in tension with strong constraints on νμ disappearance, mostly from MINOS [15] and IceCUBE [16], while attempting to fit together using a 3+1 framework [17]. Cosmic Microwave Background (CMB), together with Baryon Acoustic Oscillation (BAO) [34,35,36] and Lyα measurements [37,38] put forward significant constraint on the total neutrino mass Σmν as well as on the number of relativistic degrees of freedom Neff [39] Both of these constraints impact the viability of an additional light sterile neutrino species. While the presence of a light scalar field with negligible coupling to the inflaton have been considered in literature [55], and stringent constraint on the quartic coupling of the light field have been put [57], aspects of the non-perturbative production, especially with a small quartic self-coupling, during the preheating epoch have not been considered in details This may lead to serious issues which may destroy inflationary cosmology. Energy flow to any sector i by decay of the inflaton depends on the branching ratio defined by, Bi
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