OSQAR Annual Report 2013

Significant progresses have been achieved in 2013 in both directions targeted by the OSQAR experiments. Concerning the Vacuum Magnetic Birefringence (VMB) measurement, recent developments have allowed precise measurements of the Cotton Mouton effect of N2 gas as a function of the gas pressure within one aperture of a LHC dipole. To further gain in sensitivity and prepare the next steps, a prototype of Fabry-Perot cavity has been developed and tested for the first time across a full scale LHC dipole in the SM18 hall. For the OSQAR photon regeneration experiment, a new 15 W CW laser working at 532 nm has been installed, aligned and operated. This experiment has been run very efficiently with both new spare LHC dipoles re-commissioned on cryogenic benches in 2012. Preliminary treatments of data coming from the 2013 experimental run provide new exclusion limits for the search of scalar and pseudo-scalar light particle that go beyond the present reference ones obtained by the ALPS collaboration. Detailed and more precise analyses are ongoing.