Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π + p scattering, and at 67.3 and 87.2 MeV for π − p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

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Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch µ + → e + X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of m X = 103.9 MeV/c 2 , close to the kinematical limit. We have performed a search for the X particle by studying for the first time the very low energy part of the Michel spectrum in µ + decays. Using a HPGe detector setup at the µE4 beamline at PSI we find branching ratios BR(µ + → e + X) < 5.7 · 10 −4 (90% C.L.) for most of the region 103 MeV/c 2 < m X < 105 MeV/c 2 .

The total cross sections for pionic charge exchange on hydrogen were measured using a transmission technique on thin CH2 and C targets. Data were taken for pi- lab energies from 39 to 247 MeV with total errors of typically 2% over the Delta-resonance and up to 10% at the lowest energies. Deviations from the predictions of the SAID phase shift analysis in the 60 to 80 MeV region are interpreted as evidence for isospin-symmetry breaking in the s-wave amplitudes. The charge dependence of the Delta-resonance properties appears to be smaller than previously reported

Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch µ + → e + X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of m X = 103.9 MeV/c 2 , close to the kinematical limit. We have performed a search for the X particle by studying for the first time the very low energy part of the Michel spectrum in µ + decays. Using a HPGe detector setup at the µE4 beamline at PSI we find branching ratios BR(µ + → e + X) < 5.7 · 10 −4 (90% C.L.) for most of the region 103 MeV/c 2 < m X < 105 MeV/c 2 .