Parametrization of GPDs from t-channel string exchange in AdS spaces

TL;DR

This paper presents a novel string-inspired parametrization of nucleon GPDs valid for all skewness, leveraging conformal moments and t-channel string exchange in AdS spaces, aligning with Lorentz invariance and unitarity.

Contribution

It introduces a model-independent framework for GPDs based on AdS string exchange, accurately fitting empirical data with only five parameters and satisfying polynomiality.

Findings

Accurately models various nucleon GPDs using five parameters.

Isovector nucleon quark GPD aligns with lattice data.

Avoids deconvolution problem at any skewness.

Abstract

We introduce a string-based parametrization for nucleon quark and gluon generalized parton distributions (GPDs) that is valid for all skewness. Our approach leverages conformal moments, representing them as the sum of spin-j nucleon A-form factor and skewness-dependent spin-j nucleon D-form factor, derived from t-channel string exchange in AdS spaces consistent with Lorentz invariance and unitarity. This model-independent framework, satisfying the polynomiality condition due to Lorentz invariance, uses Mellin moments from empirical data to estimate these form factors. With just five Regge slope parameters, our method accurately produces various nucleon quark GPD types and symmetric nucleon gluon GPDs through pertinent Mellin-Barnes integrals. Our isovector nucleon quark GPD is in agreement with existing lattice data, promising to improve the empirical extraction and global analysis of nucleon GPDs in exclusive processes, by avoiding the deconvolution problem at any skewness, for the first time.