Nambu-Goldstone mesons in strong magnetic field

TL;DR

This paper investigates how strong magnetic fields affect the quark-antiquark structure of chiral mesons, revealing that GMOR relations hold for neutral mesons but break down for charged ones beyond a certain field strength, with implications for chiral perturbation theory.

Contribution

It demonstrates the limitations of GMOR relations and chiral perturbation theory for charged mesons in strong magnetic fields using a qar{q} based chiral Lagrangian approach.

Findings

GMOR relations hold for neutral mesons in strong magnetic fields.

GMOR relations are violated for charged mesons when eB > 0.2 GeV^2.

Calculated meson masses agree with lattice data in the studied regime.

Abstract

We study the q \bar q structure embedded in chiral mesons in response to external magnetic fields, using the chiral Lagrangian with q \bar q degrees of freedom derived earlier. We show that GMOR relations hold true for neutral chiral mesons, while they are violated for the charged ones for eB>sigma=0.2 GeV^2. The standard chiral perturbation theory also fails in this region. Masses of pi^+ and pi^0 mesons are calculated and compared to lattice data.