OSQAR Annual Report 2015

In 2015, the OSQAR-CHASE experiment dedicated to the search of chameleon particles has been operated using one spare LHC dipoles re-commissioned and installed on a cryogenic bench at CERN-SM18. High vacuum condition has been reached within the magnet aperture. A 18 W CW laser working at 532 nm and a new CCD detector have been installed, aligned and operated. Simulations of the expected afterglow chameleon signature have been consolidated and the data analysis is in progress. The collaboration is now focusing on the new OSQAR-CHASE proposal to further improve the experimental conditions, specially the vacuum, prior to new data taken planned for 2016. In parallel, the analysis of the OSQAR-LSW data recorded in 2014 has been finalized and accepted for publication. They provide new reference results for the exclusion limits of scalar and pseudo-scalar sub-eV axion like particle improving by a factor of about 2 the previous ones obtained by the ALPS collaboration. To further improve the sensitivity of the OSQAR-LSW experiment, the development and tests of Fabry-Perot cavities have been pursued. Discussions are in progress to speed-up such a development in collaboration with ALPS.