Search for the Hypothetical pi -> mu x Decay

Abstract

The KARMEN collaboration has reported the possible observation of a hitherto unknown neutral and weakly interacting particle x, which is produced in the decay pi -> mu + x with a mass m(x) = 33.9 MeV. We have searched for this hypothetical decay branch by studying muons from pion decay in flight with the LEPS spectrometer at the piE3 channel at PSI and find branching ratios BR(pi- to mu- anti-x) < 4e-7 and BR(pi+ to mu+ x) < 7e-8 (95\% C.L.). Together with the limit BR > 2e-8 derived in a recent theoretical paper our result would leave only a narrow region for the existence of x if it is a heavy neutrino.

10 pages, TeX (uses epsf), 3 Postscript figures uu-encoded

References in corpus (1)

• Remarks on the KARMEN Anomaly

Cited by in corpus (11)

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• Nearly degenerate heavy sterile neutrinos in cascade decay: mixing and oscillations
• A Supersymmetric Resolution of the KARMEN Anomaly
• Searching for sterile neutrinos from $\pi$ and $K$ decays
• Search for Exotic Muon Decays
• Atmospheric Sterile Neutrinos
• Space-time evolution of heavy sterile neutrinos in cascade decays
• Does the KARMEN time anomaly originate from a beam-correlated background?