Introduction to sterile neutrinos

Abstract

Model-building issues raised by the prospect of light sterile neutrinos are discussed in a pedagogical way. I first review the na\"ıve proposal that sterile neutrinos be identified with ``right handed neutrinos''. A critical discussion of the simple expedient of adding three gauge singlet fermions to the usual minimal standard model matter content is followed by an examination of right handed neutrinos in extended theories. I introduce the terminology of ``fully sterile'' and ``weakly sterile'' to classify varieties usually conflated under the sterile neutrino banner. After introducing the concepts of ``technical naturalness'' and plain ``naturalness'', the unbearable lightness of being a sterile neutrino is confronted. This problem is used to motivate mirror neutrinos, whose connection with pairwise maximal mixing is emphasised. Some brief remarks about phenomenology are made throughout. The impossibility of identifying the sole sterile neutrino of the currently favoured $2+2$ and $3+1$ phenomenological constructs as a lone gauge singlet fermion added to the minimal standard model is explained. Finally, I remark on the beauty and subtlety of light sterile neutrino cosmology.

14 pages, latex. Invited lecture at the "International School of Nuclear Physics, 23rd Course: Neutrinos in Astro, Particle and Nuclear Physics", Erice, Italy, 18-26 Sept 2001. To appear in Progress in Particle and Nuclear Physics

References in corpus (2)

• Measurement of the rate of nu_e + d --> p + p + e^- interactions produced by 8B solar neutrinos at the Sudbury Neutrino Observatory
• Cornering (3+1) sterile neutrino schemes

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• Investigation on light dark matter
• Search for Sterile Neutrinos Mixing with Muon Neutrinos in MINOS
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• KATRIN: Status and Prospects for the Neutrino Mass and Beyond
• Matter Effects in Active-Sterile Solar Neutrino Oscillations
• Wavelet Approach to Search for Sterile Neutrinos in Tritium $\beta$-Decay Spectra
• Baseline-dependent neutrino oscillations with extra-dimensional shortcuts
• Strong limits on keV-scale galactic sterile neutrino dark matter with stray light from NuSTAR after 11 years of operation
• The Impact of Assuming Flatness in the Determination of Neutrino Properties from Cosmological Data
• Roles of sterile neutrinos in particle physics and cosmology
• Last CPT-Invariant Hope for LSND Neutrino Oscillations
• All-sky limits on Sterile Neutrino Galactic Dark Matter obtained with SRG/ART-XC after two years of operations
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• The Supersymmetric $(B-L)$ model with three non-identical right-handed neutrinos
• Oscillations Beyond Three-Neutrino Mixing
• Some New Symmetric Relations and the Prediction of Left and Right Handed Neutrino Masses using Koide's Relation
• A Sterile Neutrino Search at compact materials irradiation facility