PVLAS: Vacuum Birefringence And Production And Detection Of Nearly Massless, Weakly Coupled Particles By Optical Techniques

Nearly massless particles coupling weakly to two photons constitute suitable candidates as dark matter components: experimental searches investigating this effect by optical techniques have recently been conducted. PVLAS is an experiment designed to measure the vacuum magnetic birefringence and to improve the detection sensitivity for the above particles. It is based on a very sensitive ellipsometer and a 9 T superconducting dipole magnet especially developed for this purpose. With a sensitivity of about 10^-8 rad/√Hz and an integration time of 10^6 s we plan to be able to detect a dichroism corresponding to the production of particles with a coupling constant to two photons of 10^-8 GeV^-1, provided that particle masses are less than 10^-3 eV. With our experimental parameters, the vacuum birefringence effect would give to an ellipticity of 10^-11 rad.