Results of a search for paraphotons with intense X-ray beams at SPring-8

A search for paraphotons, or hidden U(1) gauge bosons, is performed using an intense X-ray beamline at SPring-8. “Light Shining through a Wall” technique is used in this search. No excess of events above background is observed. A stringent constraint is obtained on the photon-paraphoton mixing angle, χ<8.06×10−5 (95% C.L.) for 0.04eV