Recently, the PVLAS collaboration has reported evidence for an anomalous rotation of the polarization of light in vacuum in the presence of a transverse magnetic field. This may be explained through the production of a new light spin-zero (axion-like) neutral particle coupled to two photons. The proposed ALPS (Axion-Like Particle Search) experiment is a photon regeneration experiment which exploits the photon beam of a high-power infrared laser, sent along the transverse magnetic field of a superconducting HERA dipole magnet. This setup offers a window of opportunity for a rapid and firm establishment or exclusion of the axion-like particle interpretation of the PVLAS anomaly. If this particle turns out to exist, ALPS will also allow for the measurement of its mass, parity, and coupling strength.

Currently, the technical realization and funding of ALPS are being specified after general approval by the DESY directorate on Jan. 11, 2006. Our group is involved in the challenging detection of single IR photons and in the overall data acquisition.

Further reading: ALPS webpage