Observations suggest theoretical “heavy photons” to be unlikely

New Scientist : Do photons have mass? If they did, the mass could be a possible component of the dark matter that makes up 85% of the universe’s mass. To find out, Vitor Cardoso and his colleagues at the Technical University of Lisbon in Portugal studied black holes, where matter and light undergo significant stress and extremes. If such “heavy photons” existed, when they entered the orbit of a rotating black hole they would slow the rotation through conservation of momentum. Cardoso’s team calculated the slowing effect of various possible photon masses and compared those values with the ages and rotational speeds of known supermassive black holes. The resulting upper bound for the mass of heavy photons was 10 ^-20 electronvolts, 20 orders of magnitude lighter than the lightest known particle. The researchers believe that to be so unlikely as to essentially rule out the possibility of photons with mass.