Kaon Distribution Amplitudes from Euclidean Functional QCD

TL;DR

This paper computes the kaon distribution amplitude using Euclidean functional QCD and LaMET, providing first-principles results for the kaon’s internal quark structure at high momentum.

Contribution

It introduces a novel first-principles calculation of the kaon distribution amplitude combining Euclidean functional QCD with LaMET, including new extrapolation techniques.

Findings

Kaon DA is single-peaked and asymmetric.

First and second moments of the kaon DA are 0.020(3) and 0.253(12).

Kaon quasi-DA obtained at high longitudinal momentum.

Abstract

We study the kaon quasi-distribution amplitude (quasi-DA) and distribution amplitude (DA) within the large-momentum effective theory (LaMET) combined with the first-principles functional QCD. Using quark correlation functions and the kaon Bethe-Salpeter amplitude in the Euclidean space from the 2+1 flavour functional QCD [1] as inputs, we obtain the kaon quasi DA in the large longitudinal momentum region with the contour deformation method [2] in the complex plane of momentum. By performing $1/P_z^2$ and $1/P_z^4$ order extrapolations of the kaon quasi-DA for the choices of the maximal longitudinal momentum $P_z^{\max}\in[2,2.5]$ GeV, we obtain a single-peaked and asymmetric kaon DA with the uncertainties arising from the extrapolation interval and ansatz. We find the first and second order moments of the kaon DA, $\langle \xi \rangle_K = 0.020(3)$ and $\langle \xi^2 \rangle_K = 0.253(12)$, respectively.