Test of U(1)U(1) local gauge invariance in Proca electrodynamics

An experiment for testing U(1)U(1) local gauge invariance in Proca electrodynamics has been performed by a rotating toroidal coil torsion pendulum. The expected signal, presented as the nonzero energy density of the magnetic filed vector potentials, is sought and a null result is obtained, showing the U(1)U(1) symmetry being tightly held presently.