OSQAR Annual Report 2017

In 2017, the OSQAR-CHASE experiment dedicated to the search of chameleon particles has been run with one spare LHC dipoles installed and re-commissioned on its dedicated cryogenic bench at CERN-SM18. High vacuum condition has been reached within the magnet aperture using cryo-pumping. A 18 W CW laser working at 532 nm and a state-of-the art CCD detector have been installed, aligned and operated searching for a phosphorescent signal of the vacuum permeated by the magnetic field coming from Chameleons. The analysis of the data is ongoing. In parallel, a new analysis of the OSQAR-LSW data recorded during the 2014 experimental run is being pursued. It is based on the cross-correlation method and will allow further improvement of the present reference exclusion limits obtained by OSQAR-LSW for scalar and pseudoscalar sub-eV axion like particle search. Additional gains in the sensitivity of OSQAR-LSW can be obtained by using more than 2 LHC dipoles and by developing dedicated Fabry-Perot cavities. A new French-German proposal has been submitted in 2017 to the ANR-DFG funding agencies to support these developments. Concerning OSQAR-VMB, the first phase is coming to an end. The next one requires the development of a long Fabry-Perot cavity and a revision of the optical detection scheme. An extended European initiative is being prepared within the scope of the Physic Beyond Collider (PBC) working group to measure the vacuum magnetic birefringence at CERN.