Anomalous soft photons in hadron production

Abstract

Anomalous soft photons in excess of what is expected from electromagnetic bremsstrahlung have been observed in association with the production of hadrons, mostly mesons, in high-energy K + p, π + p, π − p, pp, and e + e − collisions. We propose a model for the simultaneous production of anomalous soft photons and mesons in quantum field theory, in which the meson production arises from the oscillation of color charge densities of the quarks of the underlying vacuum in the flux tube. Because 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 soft photons during the meson production process. How the production of these soft photons may explain the anomalous soft photon data is discussed. Further experimental measurements to test the model are proposed.

An Overview of the Anomalous Soft Photons in Hadron Production

“…Wong proposed that soft photons arises in conjunction with the production of hadron in the quantum field theory of particle production in QCD2 and QED2 [21]. Such a mechanism will be discussed in more detail in subsequent sections.…”

“…While the various proposed models may explain some features of the soft photon production process, the fourth feature listed in Section 4 from recent DELPHI observations cannot be explained by almost all existing models [9,10]. As the DELPHI data reveals differential properties associated with the charged and neutral hadron multiplicities and these multiplicities depend on the isospin properties of the produced hadrons, we seek a quantum field theory description for the simultaneous production of hadrons and anomalous soft photons with explicit flavor degrees of freedom in q-q string-fragmentation that may explain this peculiar feature of the phenomenon [21].…”

“…With such a bosonization, the kinetic energy, the interaction energy, and the mass term lead to the Hamiltonian density [21]…”

Event-by-event study of space-time dynamics in flux-tube fragmentation

“…A fundamental description of the process from the basic principles of QCD is still lacking. Simplified field theoretical descriptions in terms QED2 or QCD2 in one space and one time coordinates have been presented to understand some gross features of the process [3,4,21,[29][30][31][32][33]. However, phenomenological applications of the quantum field theoretical description remain quite limited.…”

Soft photon production from real-time dynamics of jet fragmentation

“…Many theoretical models have been proposed to explain this phenomenon (for a review of earlier work, see e.g. [8]; see also [9,10,11,12,13]), however, none of them explains all the features of it. Recently, photon yield was measured in hadronic decays of the Z 0 boson by the DELPHI Collaboration [14,15].…”