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 ($\lambda =514\mathrm{}$ nm) through a transverse magnetic field. A limit of 3.5×${10}^{-10\mathrm{}}$ 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 $g_{\alpha \gamma \gamma }<3.6\mathrm{}\times {10}^{-7\mathrm{}}$ Ge${\mathrm{V}}^{-1\mathrm{}}$ at the 95% confidence level, provided $m_a<{10}^{-3\mathrm{}}$ 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 $g_{\alpha \gamma \gamma }<6.7\mathrm{}\times {10}^{-7\mathrm{}}$ Ge${\mathrm{V}}^{-1\mathrm{}}$ for the same range of particle mass.