Endpoint behavior of high-energy scattering cross sections

TL;DR

This paper analyzes how spectator interactions influence high-energy scattering cross sections near the endpoint, showing their increasing significance and factorization properties in deep-inelastic scattering and Drell-Yan processes.

Contribution

It provides a detailed power counting analysis of spectator contributions at the endpoint, including their factorization and impact on different scattering processes.

Findings

Spectator interactions become comparable to leading contributions near the endpoint.

Factorization including spectator interactions is possible for deep-inelastic scattering.

Spectator contributions are suppressed in Drell-Yan compared to double parton annihilation.

Abstract

In high-energy processes near the endpoint, there emerge new contributions associated with spectator interactions. Away from the endpoint region, these new contributions are suppressed compared to the leading contribution, but the leading contribution becomes suppressed as we approach the endpoint and the new contributions become comparable. We present how the new contributions scale as we reach the endpoint and show that they are comparable to the suppressed leading contributions in deep-inelastic scattering by employing a power counting analysis. The hadronic tensor in deep-inelastic scattering is shown to factorize including the spectator interactions, and it can be expressed in terms of the lightcone distribution amplitudes of initial hadrons. We also consider the contribution of the spectator contributions in Drell-Yan processes. Here the spectator interactions are suppressed compared to double parton annihilation according to the power counting.