Search for nearly massless, weakly coupled particles by optical techniques

We have searched for light scalar and/or pseudoscalar particles that couple to two photons by studying the propagation of a laser beam (=514 nm) through a transverse magnetic field. A limit of 3. 510^-10 rad was set on a possible optical rotation of the beam polarization for an effective path length of 2. 2 km in a 3. 25 T magnetic field. We find that the coupling g_<3. 610^-7 GeV^-1 at the 95% confidence level, provided m₀<10^-3 eV. Similar limits can be set from the absence of ellipticity in the transmitted beam. We also searched for photon regeneration in a magnetic field and found the limit g_<6. 710^-7 GeV^-1 for the same range of particle mass.