Earlier this year the PVLAS collaboration announced the possible signature of the hypothesized particle known as the axion, in an experiment to measure light polarization rotation in a magnetic field (see CERN Courier June 2006 p11 and see CERN Courier July/August 2006 p19). Now a team of researchers in Lisbon has argued that what might have been detected is not an axion, but a new effect in quantum electrodynamics (QED).

Tito Mendonça, Dias de Deus and Castelo Ferreira of the Instituto Superior Técnico in Lisbon have argued that a beam of light propagating in a slowly rotating magnetic field can give rise to an infinite tower of frequency shifts proportional to the rotation frequency. The data from PVLAS may reflect a first measurement of this effect in pure QED, rather than evidence for an axion.

Further reading

J T Mendonça, J Dias de Deus and P Castelo Ferreira 2006 http://xxx.lanl.gov/abs/hep-ph/0606099.