Experimental observation of optical rotation generated in vacuum by a   magnetic field
  We report the experimental observation of a light polarization rotation in vacuum in the presence of a transverse magnetic field. Assuming that data distribution is Gaussian, the average measured rotation is (3.9+/-0.5)e-12 rad/pass, at 5 T with 44000 passes through a 1m long magnet, with lambda = 1064 nm. The relevance of this result in terms of the existence of a light, neutral, spin-zero particle is discussed. 
E. Zavattini, G. Zavattini, G. Ruoso, E. Polacco, E. Milotti, M.   Karuza, U. Gastaldi, G. Di Domenico, F. Della Valle, R. C...