Search for photon-photon elastic scattering in the X-ray region

We report the first results of a search for real photon-photon scattering using X rays. A novel system is developed to split and collide X-ray pulses by applying interferometric techniques. A total of 6.5 x 10(5) pulses (each containing about 10(11) photons) from an X-ray Free-Electron Laser are injected into the system. No scattered events are observed, and an upper limit of 1.7 x 10(-2)4 m(2) (95% C.L.) is obtained on the photon-photon elastic scattering cross section at 6.5 keV. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.orgilicensesiby/3.0/). Funded by SCOAP(3).