Neutral-pion reactions induced by chiral anomaly in strong magnetic fields

TL;DR

This paper explores how strong magnetic fields influence neutral pion decay and production, revealing a shift from photon decay to dilepton decay modes and predicting anisotropic dilepton spectra as experimental signatures.

Contribution

It introduces the impact of chiral anomaly in strong magnetic fields on neutral pion decay channels and proposes a novel mechanism for anisotropic dilepton production in heavy-ion collisions.

Findings

Neutral pions decay predominantly into dileptons in strong magnetic fields.

Virtual photons can convert into neutral pions after passing through magnetic fields.

Anisotropic dilepton spectra can serve as signatures of magnetic field effects.

Abstract

We investigate decay and production of neutral pions in strong magnetic fields. In the presence of strong magnetic fields, transition between a neutral pion and a virtual photon becomes possible through the triangle diagram relevant for the chiral anomaly. We find that the decay mode of a neutral pion into two photons cannot persist in the dominant mode in strong magnetic fields, and that decay into a dilepton instead dominates over the other modes. We also investigate the effects of magnetic fields on prompt virtual photons created in ultrarelativistic heavy-ion collisions. There is no anisotropy in the spectrum at the stage of creation of prompt virtual photons, but after traversing the strong magnetic field that is induced perpendicularly to the reaction plane, virtual photons turn into neutral pions, leading to an anisotropic spectrum of dileptons as a feasible signature in the measurement.