  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. In this
letter-of-intent, we propose to test this hypothesis by setting up 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. The proposed ALPS (Axion-Like Particle Search) experiment offers
a window of opportunity for a rapid firm establishment or exclusion of the
axion-like particle interpretation of the anomaly published by PVALS. It will
also allow for the measurement of mass, parity, and coupling strength of this
particle. [The experiment has been approved by the DESY directorate on January
11, 2007.]
