Minimal models with light sterile neutrinos

Abstract

We study the constraints imposed by neutrino oscillation experiments on the minimal extensions of the Standard Model (SM) with $n_R$ gauge singlet fermions ("right-handed neutrinos"), that can account for neutrino masses. We consider the most general coupling to SM fields of the new fields, in particular those that break lepton number and we do not assume any a priori hierarchy in the mass parameters. We proceed to analyze these models starting from the lowest level of complexity, defined by the number of extra fermionic degrees of freedom. The simplest choice that has enough free parameters in principle (i.e. two mass differences and two angles) to explain the confirmed solar and atmospheric oscillations corresponds to $n_R=1$. This minimal choice is shown to be excluded by data. The next-to-minimal choice corresponds to $n_R=2$. We perform a systematic study of the full parameter space in the limit of degenerate Majorana masses by requiring that at least two neutrino mass differences correspond to those established by solar and atmospheric oscillations. We identify several types of spectra that can fit long-baseline reactor and accelerator neutrino oscillation data, but fail in explaining solar and/or atmospheric data. The only two solutions that survive are the expected seesaw and quasi-Dirac regions, for which we set lower and upper bounds respectively on the Majorana mass scale. Solar data from neutral current measurements provide essential information to constrain the quasi-Dirac region. The possibility to accommodate the LSND/MiniBoone and reactor anomalies, and the implications for neutrinoless double-beta decay and tritium beta decay are briefly discussed.

32 pages, 15 figures. Misprints and a small error corrected, references added. Conclusions unchanged

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Cited by in corpus (32)

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• Can heavy neutrinos dominate neutrinoless double beta decay?
• The minimal 3+2 neutrino model versus oscillation anomalies
• Fundamental physics with the diffuse supernova background neutrinos
• $N_{\mathrm{eff}}$ in low-scale seesaw models versus the lightest neutrino mass
• Light Sterile Neutrinos: Status and Perspectives
• Heavy Sterile Neutrinos in Tau Decays and the MiniBooNE Anomaly
• Light Sterile Neutrinos and Short Baseline Neutrino Oscillation Anomalies
• Beta and Neutrinoless Double Beta Decays with KeV Sterile Fermions
• Naturally small Yukawa couplings from trans-Planckian asymptotic safety
• Constraining the (Low-Energy) Type-I Seesaw
• Disentangling left and right-handed neutrino effects in $B\to K^{(\ast )}\nu \nu$
• Low-scale seesaw models versus $N_{\mathrm{eff}}$
• Neutrino Masses from the Top Down
• Minimal 3+2 sterile neutrino model at LBNE
• PROSPECT-II Physics Opportunities
• $pp$ Solar Neutrinos at DARWIN
• Accessible Lepton-Number-Violating Models and Negligible Neutrino Masses
• Constraining super-light sterile neutrinos at Borexino and KamLAND
• Neutrino mixing, interval matrices and singular values
• Thermal effects in freeze-in neutrino dark matter production
• Sterile Neutrino Anarchy
• Leptogenesis in GeV scale seesaw models
• Learning about flavour structure from tau to ell gamma and mu to e gamma?
• Reconstructing Seesaws
• New physics from oscillations at the DUNE near detector, and the role of systematic uncertainties
• Dark Matter Phenomenology: Sterile Neutrino Portal and Gravitational Portal in Extra-Dimensions