Long-Range Lepton Flavor Interactions and Neutrino Oscillations

Abstract

Recent results from the MINOS accelerator neutrino experiment suggest a possible difference between nu_mu and anti-nu_mu disappearance oscillation parameters, which one may ascribe to a new long-distance potential acting on neutrinos. As a specific example, we consider a model with gauged B - L_e - 2 L_tau number that contains an extremely light new vector boson m_Z' < 10^-18 eV and extraordinarily weak coupling alpha' < 10^-52. In that case, differences between nu_mu to nu_tau and anti-nu_mu to anti-nu_tau oscillations can result from a long-range potential due to neutrons in the Earth and the Sun that distinguishes nu_mu and nu_tau on Earth, with a potential difference of ~ 6*10^-14 eV, and changes sign for anti-neutrinos. We show that existing solar, reactor, accelerator, and atmospheric neutrino oscillation constraints can be largely accommodated for values of parameters that help explain the possible MINOS anomaly by this new physics, although there is some tension with atmospheric constraints. A long-range interaction, consistent with current bounds, could have very pronounced effects on atmospheric neutrino disappearance in the 20-50 GeV range that will be studied with the IceCube DeepCore array, currently in operation, and can have a significant effect on future high-precision long-baseline oscillation experiments that aim for +- 1% sensitivity, in nu_mu and anti-nu_mu disappearance, separately. Together, these experiments can extend the reach for new long-distance effects well beyond current bounds and test their relevance to the aforementioned MINOS anomaly. We also point out that long-range potentials originating from the Sun could lead to annual modulations of neutrino data at the percent level, due to the variation of the Earth-Sun distance. A similar phenomenology is shown to apply to other potential new gauge symmetries such as L - 3 L_tau and B - 3 L_tau.