Optical production and detection of dark matter candidates

TL;DR

This paper discusses the PVLAS experiment's optical setup designed to detect or constrain light scalar and pseudoscalar particles, such as axions, which are potential dark matter candidates, through vacuum magnetic birefringence measurements.

Contribution

It presents the design and capabilities of a highly sensitive optical ellipsometer for detecting dark matter candidates via vacuum magnetic birefringence.

Findings

Set new limits on mass and coupling constants of light scalar/pseudoscalar particles.

Demonstrated the apparatus's sensitivity to small rotations and ellipticities.

Potential to detect or exclude certain dark matter particle models.

Abstract

The PVLAS collaboration is at present running, at the Laboratori Nazionali di Legnaro of I.N.F.N., Padova, Italy, a very sensitive optical ellipsometer capable of measuring the small rotations or ellipticities which can be acquired by a linearly polarized laser beam propagating in vacuum through a transverse magnetic feld (vacuum magnetic birefringence). The apparatus will also be able to set new limits on mass and coupling constant of light scalar/pseudoscalar particles coupling to two photons by both producing and detecting the hypothetical particles. The axion, introduced to explain parity conservation in strong interactions, is an example of this class of particles, all of which are considered possible dark matter candidates. The PVLAS apparatus consists of a very high finesse (> 140000), 6.4 m long, Fabry-Perot cavity immersed in an intense dipolar magnetic field (~6.5 T). A linearly polarized laser beam is frequency locked to the cavity and analysed, using a heterodyne technique, for rotation and/or ellipticity acquired within the magnetic field.