Nucleon Structure from Basis Light-Front Quantization : Status and Prospects

TL;DR

This paper reviews recent progress in understanding nucleon structure using the Basis Light-Front Quantization framework, which is a relativistic, nonperturbative approach to solving quantum chromodynamics and predicting nucleon properties.

Contribution

It reports on extending BLFQ to include higher Fock sectors and computing nucleon wavefunctions directly from the QCD Hamiltonian, advancing first-principles predictions of nucleon structure.

Findings

Successful description of key nucleon observables.

Inclusion of gluonic contributions to nucleon structure.

Qualitative agreement with experimental data.

Abstract

We review recent advancements in understanding nucleon structure within the Basis Light-Front Quantization (BLFQ) framework--a fully relativistic, nonperturbative approach to solving quantum field theories. In its initial phase, we start with the leading Fock sector $|qqq\rangle$ and an effective light-front Hamiltonian incorporating confinement and one-gluon exchange within which BLFQ can already successfully describe key nucleon observables. The framework has since been extended to include the next-to-leading Fock sector $|qqqg\rangle$, enabling studies of gluonic contributions to the nucleon's internal structure, including gluon helicity, orbital angular momentum, and three-dimensional imaging through generalized and transverse momentum dependent parton distributions (GPDs and TMDs). Most recently, BLFQ has achieved a significant milestone by computing nucleon light-front wavefunctions as eigenstates of the QCD Hamiltonian without an explicit confining potential. These calculations, including Fock sectors up to $|qqqq\bar{q}\rangle$, further develop the path to first-principles predictions of quark and gluon matter densities, helicity and transversity distributions, and spin observables, showing qualitative agreement with experimental and phenomenological results. Together, these developments highlight BLFQ's growing capacity to provide an increasingly complete and realistic picture of nucleon structure grounded in QCD.