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, chi < 8.06 x 10(-5) (95% C.L.) for 0.04 eV < m(gamma') < 26 keV. (c) 2013 Elsevier B.V. All rights reserved.