PVLAS results
  The PVLAS experiment has built an apparatus to measure rotations and ellipticities induced by a transverse magnetic field onto linearly polarized laser light.Available results can be interpreted as observation of an unexpectedly large rotation effect between 10-7 and 4 10-7rad. If this rotation is due to the existence of a light spin zero boson of mass m and coupling to two photons 1/M, the ball-park values of the boson mass parameters are m=1meV and M=10+6GeV. 
Ugo Gastaldi