Abstract
The MiniBooNE collaboration recently reported further evidence for the existence of sterile neutrinos, implying substantial mixing with the left-handed active neutrinos and at a comparable mass scale. I argue that while sterile neutrinos may arise naturally in large volume string models, they prove more of a challenge in heterotic-string models that replicate the Grand Unified Theory structure of the Standard Model matter states. Sterile neutrinos in heterotic-string models may imply the existence of an additional Abelian gauge symmetry of order 10–100 TeV.
Highlights
The MiniBooNE collaboration recently reported further evidence for the existence of sterile neutrinos [1]
In this paper I argued that sterile neutrinos arise naturally in large volume scenarios and by implication in string constructions in which the gravitational scale may be as low as the TeV scale
The precise nature of the sterile neutrinos in these constructions needs to be scrutinised, but it is clear that the sterile neutrinos in these models can affect various experimental observables that are being explored in contemporary experiments, e.g. lepton universality [37,38,39]
Summary
The MiniBooNE collaboration recently reported further evidence for the existence of sterile neutrinos [1]. While sterile neutrinos may arise naturally in large volume scenarios, they present more of a challenge in heterotic-string models that replicate the matter structure of Grand Unified Theories (GUTs). It should, be stressed that the experimental and phenomenological analysis in this regard is far from settled [8], and highlights the urgency for further experimental data to resolve the question. An alternative to the seesaw mechanism is the possibility that neutrinos obtain their mass via electroweak symmetry breaking In this case sterile neutrinos naturally arise as right-handed neutrinos and mirrors the mass generation of the Standard Model charged sector. A highly non-trivial construction that enables an additional E6 Z to remain unbroken below the string scale was presented in Ref. [33], and utilises self-duality under the spinor-vector duality symmetry of Refs. [34,35,36]
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