Multi-partonic interactions and the virtuality expansion in deep inelastic scattering

Tuesday, 23 September 2025 at 10:45

The KLN theorem establishes that infrared divergences in parton‑model diagrams cancel when summed alongside diagrams that account for the simultaneous hard interaction of multiple partons within the same hadron. In this talk, I will present a perturbative model that naturally accounts for these additional diagrams using the "simplest clustering criterion", as well as a realistic notion of virtuality expansion for observables computed within it. I will explore its equivalence with the parton model via a direct next‑to‑leading‑order calculation of the inclusive deep‑inelastic‑scattering cross‑section. In this context, I will also discuss the appearance of a "doubled optical theorem" as well as the analytic tools essential for the calculation, and in particular those relating to the evaluation of iterated discontinuities of Feynman diagrams. I will conclude by outlining how to extend the model to hadronic collisions.

Capatti.pdf (PDF, 9 MB)