Determination of the 2p-1s transition energy and strong interaction shift in pionic hydrogen using crystal diffraction

The 2p-1s atomic transition in pionic hydrogen has been studied with the help of a point-focusing graphite diffraction spectrometer. The transition energy was measured to be E(2p-1s)=2433.5±1.7 eV. From this result a strong interaction shift of -3.9±1.7 eV was derived. The Kα x-ray yield in the 2.7 atm hydrogen target at 40 K was found to be 0.025±0.013 per stopped pion

Neutrino-oscillation experiments at the Gösgen nuclear power reactor

A search for neutrino oscillations has been conducted at the 2800-MW (thermal) nuclear power reactor in Gösgen (Switzerland), providing 5×10^20 electron antineutrinos per second. The energy spectrum of the antineutrinos was measured at three distances, 37.9, 45.9, and 64.7 m, from the reactor core. The detection of the neutrinos is based on the reaction ν¯e+p→e++n. Roughly 10^4 antineutrinos were registered at each of the three measuring positions. The measured spectra are analyzed in terms of a two-neutrino oscillation model and the results are represented as exclusion plots for the oscillation parameters Δm^2 and sin^2(2theta). Two analyses are performed: Analysis A relies exclusively on the data measured at the three different distances; analysis B combines the measured data with additional information, in particular with the reactor antineutrino spectrum as derived from independent β-spectroscopic measurements. Both analyses show that the data are consistent with the absence of neutrino oscillations, and rule out large regions of parameters (Δm2,theta). The resulting limits on the oscillation parameters are Δm^25 eV^2