2006/11/28 by Sheng-Jui Chen, Sheng‐Jui Chen, Hsien-Hao Mei +1 · 7 citations
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #astro-ph #gr-qc #hep-ex
paper · pdf · doi:10.1142/s0217732307025844
published as Mod.Phys.Lett.A22:2815-2831,2007 · 21 pages, 13 figures, submitted to Modern Physics Letters
arxiv created 2006/11/28 · openalex publication_date 2007/12/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A number of experiments are underway to detect vacuum birefringence and dichroism — PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical interpretations of this result include a possible pseudoscalar–photon interaction and the existence of millicharged fermions. Here, we report the progress and first results of Q & A (QED [quantum electrodynamics] and Axion) experiment proposed and started in 1994. We use a 3.5-m high-finesse (around 30,000) Fabry–Perot prototype detector extendable to 7-m with the cavity mirrors suspended using X-pendulum-double pendulums. To polarize the vacuum, we use a 2.3-T dipole permanent magnet rotated at 5–10 rev/s, with 27-mm-diameter clear borehole and 0.6-m field length. Our ellipsometer/polarization-rotation-detection-system is formed by a pair of Glan–Taylor type polarizing prisms with extinction ratio lower than 10 -8 together with a polarization modulating Faraday Cell with/without a quarter wave plate. Our first results give (-0.2 ± 2.8) × 10 -13 rad/pass with 18,700 passes through a 2.3 T 0.6 m long magnet for vacuum dichroism measurement. We present our experimental limit on pseudo-scalar-photon interaction and millicharged fermions.