Coherent production/detection of light scalars/pseudoscalars and QED vacuum polarization

We searched for light scalars/pseudoscalars (e.g., axions) that couple to two photons using three different techniques: (1) Optical rotation, where a polarized laser beam enters a dipole magnetic field region. The production of scalars/pseudoscalars has an effect the rotation of the polarization which is detected by an analyzer system giving a limit [ital g][sub [alpha][gamma][gamma]][lt]3.6[times]10[sup [minus]7] GeV[sup [minus]1], for [ital m][sub [ital a]][lt]10[sup [minus]3] eV. (2) Photon regeneration experiment, where the particles are generated in one magnet by the polarized laser beam, travel through a wall and reconvert back to the original photons inside another magnet where they are detected by a photomultiplier, giving a limit to [ital g][sub [alpha][gamma][gamma]][lt]6.7[times]10[sup [minus]7] GeV[sup [minus]1] for the same mass range as above. (3) Finally we searched for scalars/pseudoscalars coming from the sun, looking at the back of a dipole magnet pointing at the setting sun, with an x-ray detector. The limit obtained this way is [ital g][sub [alpha][gamma][gamma]][lt]3.7[times]10[sup [minus]9] GeV[sup [minus]1], provided [ital m][sub [ital a]][lt]0.1 eV.