Transverse Structure of the Kaon: A light-front Hamiltonian Approach

TL;DR

This paper uses a light-front Hamiltonian approach within the BLFQ framework to compute and analyze the transverse-momentum-dependent and collinear parton distribution functions of the kaon, including twist-2 and twist-3 contributions, revealing Fock-sector interference effects.

Contribution

It provides the first theoretical predictions of kaon subleading-twist TMDs that explicitly include Fock-sector interference effects beyond the Wandzura-Wilczek approximation.

Findings

Twist-2 PDFs agree with JAM global analysis.

Genuine twist-3 contributions from quark-gluon correlations are identified.

First calculation of kaon TMDs including Fock-sector interference.

Abstract

We employ the Basis Light-Front Quantization (BLFQ) framework to compute the leading-twist (twist-2) and subleading-twist (twist-3) transverse-momentum-dependent parton distribution functions (TMDs) of the kaon. The light-front wave functions are obtained by diagonalizing a light-front QCD Hamiltonian that includes quark-antiquark (|q\bar{q}\rangle) and quark-antiquark-gluon (|q\bar{q}g\rangle) Fock components together with a three-dimensional confinement. Using the QCD equations of motion, the twist-3 TMDs are decomposed into twist-2 constributions and genuine twist-3 terms, the latter encoding quark-quark-gluon correlations beyond the probabilistic picture. These genuine twist-3 constributions arise from the interference between the |q\bar{q}\rangle and |q\bar{q}g\rangle sectors, which are usually negelected in the Wandzura-Wilczek approximation. This work provides the first theoretical predictions of kaon subleading-twist TMDs that explicitly account for Fock-sector interference. In addition, we present results for the kaon's twist-2 and twist-3 collinear parton distribution functions (PDFs). The twist-2 PDFs are found to be in good agreement with the recent global analysis by the JAM collaboration.