Chameleon Vector Bosons

We show that for a force mediated by a vector particle coupled to a conserved U (1) charge, the apparent range and strength can depend on the size and density of the source, and the proximity to other sources. This "chameleon" effect is due to screening from a light charged scalar. Such screening can weaken astrophysical constraints on new gauge bosons. As an example we consider the constraints on chameleonic gauged B −L. We show that although Casimir measurements greatly constrain any B − L force much stronger than gravity with range longer than 0.1µm, there remains an experimental window for a long range chameleonic B − L force. Such a force could be much stronger than gravity, and long or infinite range in vacuum, but have an effective range near the surface of the earth which is less than a micron