High-energy ππ scattering without and with photon radiation

We discuss the processes pi pi - pi pi and pi pi -pi pi gamma from a general quantum field theory (QFT) point of view. In the soft-photon limit where the photon energy omega - 0 we study the theorem due to F.E. Low. We confirm his result for the 1/omega term of the pi pi -pi pi gamma amplitude but disagree for the omega 0 term. We analyze the origin of this discrepancy. Then we calculate the amplitudes for the above reactions in the tensorPomeron model. We identify places where anomalous soft photons could come from. Three soft-photon approximations (SPAs) are introduced. The corresponding SPA results are compared to those obtained from the full tensor-Pomeron model for c.m. energies p s = 10 GeV and 100 GeV. The kinematic regions where the SPAs are a good representation of the full amplitude are determined. Finally we make some remarks on the type of fundamental information one could obtain from high-energy exclusive hadronic reactions without and with soft photon radiation.

Automated summary

In this paper, we discuss the processes pi pi - pi pi and pi pi - pi pi gamma from the perspective of quantum field theory (QFT). We study the theorem proposed by F.E. Low in the soft-photon limit and confirm his result for the 1/omega term. However, we disagree on the omega=0 term and investigate the discrepancy. Additionally, we calculate the amplitudes for these reactions using the tensor-Pomeron model and identify possible sources of anomalous soft photons. We introduce three soft-photon approximations (SPAs) and compare their results with those from the full model. The kinematic regions where the SPAs provide accurate representations of the full amplitude are determined. Finally, we discuss the fundamental information that can be obtained from high-energy exclusive hadronic reactions with and without soft photon radiation.