Production of high energy photons via inverse Compton scattering at SPring-8

Compton back-scattering of a laser light by the electrons circulating in Synchrotron Radiation (SR) facilities was used to provide high energy polarized photons. For this purpose, a new facility for GeV photon beams in the energy range of Eγ=1.5-3.5 GeV has been constructed at SPring-8. The GeV photons are produced via Compton backscattering, and are used to study the sub-nucleonic structure of the nucleon. The main subject of this project is to search for the quark behavior in the nucleon-the building blocks of nucleons. Fundamental role of quark in nucleon or in a nucleus will be studied as the current topics to reveal the underlying basic principle. This SPring-8 project called Laser-Electron-Photon (LEP) project offers an unique opportunity to study the nucleon structure in view of the quark physics. Using the Compton backscattered photons induced by a short-wave-length laser light, the polarized GeV photons with the maximum energy of 2.4 GeV and a low emittance are generated. This special feature makes real-photon experiments complementary with electron-scattering experiments. The detector called the LEPS spectrometer is especially designed and constructed to detect the forward events. The results from the latest experiment are shown. (author)