${\pi }^0$-$\gamma$ mixing in the presence of a strong magnetic field

Abstract

We analyze the mixing between the ${\pi }^0$ meson and the photon in the presence of a strong uniform magnetic field, in the context of a two-flavor Nambu-Jona-Lasinio model. It is shown that only one specific photon polarization state can get mixed with the ${\pi }^0$ state, a fact that can be understood on general grounds. For magnetic fields with values up to 1 GeV${}^2$/e, it is found that the effect of the mixing on the pion mass and pion-quark couplings is relatively small (below a level of 15%), which is at variance with previous results reported in the literature.

19 pages, 2 figures