Searching for a sterile neutrino that mixes predominantly with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>ν</mml:mi><mml:mi>τ</mml:mi></mml:msub></mml:math> at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> factories
Claudio Dib, Juan Carlos Helo, M. Nayak, Nicolás A. Neill, A. Soffer, J. A. Zamora Saa
Abstract
The phenomenon of neutrino flavor oscillations motivates searches for sterile neutrinos in a broad range of masses and mixing-parameter values. A sterile neutrino $N$ that mixes predominantly with the $\ensuremath{\tau}$ neutrino is particularly challenging experimentally. To address this challenge, we propose a new method to search for a ${\ensuremath{\nu}}_{\ensuremath{\tau}}$-mixing $N$ that is lighter than the $\ensuremath{\tau}$ lepton. The method uses the large ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ samples collected at $B$-factory experiments to produce the $N$ in $\ensuremath{\tau}$-lepton decays. We exploit the long lifetime of a sterile neutrino in this mass range to suppress background and apply kinematic and vertexing constraints that enable measuring the sterile-neutrino mass. Estimates for the sensitivities of the BABAR, Belle, and Belle II experiments are calculated and presented.