Limits on low energy photon-photon scattering from an experiment on magnetic vacuum birefringence

Experimental bounds on induced vacuum magnetic birefringence can be used to improve present photon-photon scattering limits in the electronvolt energy range. Measurements with the Polarizzazione del Vuoto con Laser apparatus [E. Zavattini , Phys. Rev. D 77, 032006 (2008)] at both lambda=1064 and 532 nm lead to bounds on the parameter A(e), describing nonlinear effects in QED, of A(e)((1064))< 6.6x10(-21) T-2@1064 nm and A(e)((532))< 6.3x10(-21) T-2@532 nm, respectively, at 95% confidence level, compared to the predicted value of A(e)=1.32x10(-24) T-2. The total photon-photon scattering cross section may also be expressed in terms of A(e), setting bounds for unpolarized light of sigma((1064))(gamma gamma)< 4.6x10(-62) m(2) and sigma((532))(gamma gamma)< 2.7x10(-60) m(2). Compared to the expected QED scattering cross section these results are a factor of similar or equal to 2x10(7) higher and represent an improvement of a factor about 500 on previous bounds based on ellipticity measurements and of a factor of about 10(10) on bounds based on direct stimulated scattering measurements.