Link perturbative soft-theorem results to the non-perturbative regime

Establish a theoretical connection between perturbative QCD calculations of loop-corrected soft-photon emission—specifically the three-loop corrections of order α_s^3/ω to the leading-power term and the one-loop α_s log(ω) corrections to the next-to-leading-power term—and the non-perturbative dynamics relevant for soft-photon production and hadronization in hadronic collisions, in order to extend predictive power beyond the perturbative domain.

Background

Within the survey of theoretical approaches to the soft-photon puzzle, the paper reviews recent perturbative QCD advances on soft theorems, including a three-loop correction of order α_s^3/ω to the leading-power term and one-loop logarithmic corrections to the next-to-leading-power term. These results provide refined control in the perturbative regime with massless quarks.

However, the soft-photon excess observed experimentally is believed to involve significant non-perturbative QCD physics, especially hadronization. The authors explicitly state that connecting the perturbative results to this non-perturbative regime remains unresolved, highlighting a key theoretical gap that must be bridged to understand anomalous soft-photon production.