The connection between photon mass andB (3) : The poincaré group

The longitudinal vacuum fieldB⁽³⁾ is an experimental observable which produces by magnetization a well-defined square-root beam power density dependence. Its longitudinal polarization implies that the helicities of the photon are +1, 0, and –1, and that the little group of the Poincaré group is the rotation group 0(3) of a massive boson. The mass of the photon (m) is therefore related directly toB⁽³⁾ through the Proca equation, and it is concluded that experimental evidence forB⁽³⁾ is also evidence for finitem.