T. Namba

Indications of neutrino oscillation in a 250 km long-baseline experiment.

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Direct search for solar axions by using strong magnetic field and x-ray detectors

We have searched for axions which could be produced in the solar core by exploiting their conversion to X rays in a strong laboratory magnetic field. The signature of the solar axion is an increase in the rate of the X rays detected in a magnetic helioscope when the sun is within its acceptance. From the absence of such a signal we set a 95% confidence level limit on the axion coupling to two photons

SNEWS: the SuperNova Early Warning System

g_{a\gamma\gamma}\equiv 1/M < 6.0\times 10^{-10}

Direct observation of the hyperfine transition of ground-state positronium.

GeV

New Precision Measurement of Hyperfine Splitting of Positronium

^{-1}

The OVAL experiment: A new experiment to measure vacuum magnetic birefringence using high repetition pulsed magnets

, provided the axion mass

Search for photon–photon elastic scattering in the X-ray region

m_a<0.03

New Experiment for the First Direct Measurement of Positronium Hyperfine Splitting with Sub-THz Light

eV. The limit on the coupling is factor 4.5 more stringent than the recent experimental result. This is the first experiment whose sensitivity to

An X-ray detector using PIN photodiodes for the axion helioscope

g_{a\gamma\gamma}

Probing Physics in Vacuum Using an X-ray Free-Electron Laser, a High-Power Laser, and a High-Field Magnet

is higher than the limit constrained by the solar age consideration.