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Published August 1, 2012 | Published + Accepted Version
Journal Article Open

Neutrino phenomenology in a 3+1+1 framework

Abstract

Evidence continues to grow in the MiniBooNE (MB) antineutrino mode supporting a low-energy excess compatible with the MB neutrino mode and possibly also confirming the results of the LSND experiment. At least one sterile neutrino is required to explain the anomalies consistent with the observations of other experiments. At the same time, there is a strong tension between the positive signals of LSND and MB and the null results of ν_e and ν_μ disappearance experiments. We explore a scenario, first proposed in [A. E. Nelson, Phys. Rev. D 84, 053001 (2011).], where the presence of an additional heavy sterile neutrino (with mass well above an eV) can alleviate tension between LSND, MB and the null results of disappearance experiments. We compare and contrast this 3+1+1 scenario with the more standard 3+1 scenario and carry out global fits to all oscillation data including new 2011 MB ṽ data. We find that the tension can be somewhat alleviated and that a phenomenologically viable window for the heavy neutrino, consistent with rare decays and big bang nucleosynthesis constraints, can be found if the fifth neutrino has a mass of order 0.3 – 10 GeV. We also find, however, that the 2011 MB ṽ data exacerbates the tension with null experiments in both the 3+1 and 3+1+1 models when the lowest energy bins are included, resulting in little improvement in the global fit. We also discuss the implications of an additional neutrino for the reactor and gallium anomalies, and show that an oscillation explanation of the anomalies is disfavored by cosmological considerations, direct searches, and precision electroweak tests.

Additional Information

© 2012 American Physical Society. (Received 1 June 2012; published 30 August 2012) We thank Ann Nelson and Tomer Volansky for discussions. We would also like to thank Enrique Fernandez Martinez, Oleg Ruchayskiy, and Jinrui Huang for pointing out some additional bounds relevant to the parameter space of Fig. 5. The work of E. K. is supported in part by a grant from the Israel Science Foundation. The work of K. M. Z. and S. D. M. is supported by NSF CAREER PHY 1049896, and NASA Astrophysics Theory Program Grant No. NNX11AI17G.

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Published - PhysRevD.86.033015.pdf

Accepted Version - 1205.1791.pdf

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