Abstract
In the present work of the PIENU experiment, heavy neutrinos were sought in pion decays π+→μ+ν at rest by examining the observed muon energy spectrum for extra peaks in addition to the expected peak for a light neutrino. No evidence for heavy neutrinos was observed. Upper limits were set on the neutrino mixing matrix |Uμi|2 in the neutrino mass region of 15.7–33.8 MeV/c2, improving on previous results by an order of magnitude.
Highlights
Neutrino oscillations indicate that at least two of the known neutrinos are massive, requiring the original Standard Model to be expanded
MeV neutrinos could be accommodated in the νMSM to explain the 7Li abundance [7] or, with the addition of a MeV scalar, to obtain consistent results for anomalies in neutrino experiments [8]
Heavy neutrinos mixing with the muon neutrino in the mass region 1–400 MeV/c2 have been sought by accelerator-based experiments studying pion [11,12,13,14] and kaon decays [15,16,17]
Summary
Neutrino oscillations indicate that at least two of the known neutrinos are massive, requiring the original Standard Model to be expanded. Heavy neutrinos mixing with the muon neutrino in the mass region 1–400 MeV/c2 have been sought by accelerator-based experiments studying pion [11,12,13,14] and kaon decays [15,16,17]. Heavy neutrinos in the mass region 30–33.9 MeV/c2 were sought in pion decay by Bryman and Numao [12], providing upper limits of 10−3–10−4; this search was limited by background coming from pion decays in flight (π DIF). The present search for heavy neutrinos was based on measurement of the muon kinetic energy in π + → μ+ν decays at rest. The leading backgrounds arising from accidental particles and π DIF were suppressed using waveform and tracking information to identify extra activity in the detector system, and the statistics were improved by an order of magnitude over previous experiments
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
