Tomography of high-twist proton structure through $ep$ elastic scattering

TL;DR

This paper investigates high-twist effects in proton form factors using perturbative QCD, revealing the importance of endpoint regions and resummation effects for understanding proton structure at intermediate momentum transfers.

Contribution

It presents the first high-twist analysis of proton form factors in ep elastic scattering, extracting and verifying proton LCDAs up to twist 6 with implications for three-dimensional proton structure.

Findings

Endpoint enhancement is crucial for scaling behavior at intermediate Q^2.

Proton LCDAs up to twist 6 are extracted and validated.

Resummation effects tame endpoint contributions, improving perturbative predictions.

Abstract

We present the first high-twist study of the proton form factors $F_{1,2}(Q^2)$ in $ep$ elastic scattering based on the perturbative QCD $k_T$ factorization, $Q^2$ being momentum transfer squared. It is motivated by unexpectedly large higher-power contributions from subleading-twist light-cone distribution amplitudes (LCDAs), which are attributed to the enhancement in endpoint regions of parton momentum fractions. We highlight that the endpoint enhancement, tamed by the $k_T$ resummation effect, is crucial for accommodating the approximate scaling behavior of the $Q^4F_1(Q^2)$ data at intermediate $Q^2\sim {\cal O}(10)$ GeV$^2$. The proton LCDAs up to twist 6 are then extracted, and verified by the charge-parity asymmetries observed in hadronic heavy baryon decays. Our work provides new insights into the proton three-dimensional structure and manifests the precision requirement for reliable perturbative analyses of baryonic exclusive processes.