Reconciling the CAST and PVLAS Results

The PVLAS experiment has recently claimed evidence for an axionlike particle in the milli-electron-volt mass range with a coupling to two photons that appears to be in contradiction with the negative results of the CAST experiment searching for solar axions. The simple axion interpretation of these two experimental results is therefore untenable and it has posed a challenge for theory. We propose a possible way to reconcile these two results by postulating the existence of an ultralight pseudoscalar particle interacting with two photons and a scalar boson and the existence of a low scale phase transition in the theory.

Figure 1

Diagram for photon-photon scattering.

Figure 2

The annihilation process $e^{+}{e}^{-}\to \gamma +a+\varphi$.