  Productions of soft photon with low transverse momenta in high-energy
hadron-hadron collisions and $e^+$-$e^-$ annihilations indicate that they are
consistently produced in excess of what are predicted by electromagnetic
bremsstrahlung when hadrons (mostly mesons) are produced, but they agree with
electromagnetic bremsstrahlung predictions in the absence of hadron production.
These excess soft photons are called anomalous soft photons. The occurrence of
anomalous soft photons in association with hadron production reveals the
presence of additional QED soft photon sources in QCD hadron production. Many
different models have been proposed to explain the anomalous soft production.
We shall examine specifically a quantum field theory of simultaneous meson and
soft photon production in QCDxQED in which the meson production arises from the
oscillation of color charge densities of the quarks of the underlying vacuum in
a flux tube. As a quark carries both a color charge and an electric charge, the
oscillation of the color charge densities will be accompanied by the
oscillation of electric charge densities, which will in turn lead to the
simultaneous production of anomalous soft photons during the meson production
process.
