Kaon gravitational form factors and mechanical structure in a three-flavor NJL model
Abstract
We investigate the gravitational form factors (GFFs) of the kaon in a proper-time-regularized three-flavor Nambu--Jona-Lasinio model. We treat the kaon as a light--strange pseudoscalar bound state and evaluate its energy--momentum-tensor matrix element using a dressed quark--graviton vertex. By retaining the interaction-induced contact contribution alongside the quark triangle diagrams, we preserve the gravitational Ward--Takahashi identity and ensure the conservation of the total energy--momentum tensor. We determine the light- and strange-quark contributions to the kaon GFFs, contrast them with the corresponding pion results, and extract the associated pressure and shear-force distributions, together with the Breit-frame and transverse light-front mass radii. Explicit flavor-symmetry breaking dictates that the strange sector carries a larger share of the kaon momentum and mechanical response. Consequently, compared to the pion, the kaon exhibits a less negative D-term and more compact mechanical distributions, featuring enhanced central pressure and shear. We further show that a Ward--Takahashi-identity-preserving reduction of the C-term projection is essential for maintaining the pion low-energy theorem in proper-time regularization.
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BibTeX
@misc{liu2026kaon,
title = {{Kaon gravitational form factors and mechanical structure in a three-flavor NJL model}},
author = {Zhibo Liu and Hiroaki Abuki},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29848},
eprint = {2608.29848},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29848},
note = {CC0},
}
RIS
TY - UNPB
TI - Kaon gravitational form factors and mechanical structure in a three-flavor NJL model
AU - Zhibo Liu
AU - Hiroaki Abuki
PY - 2026
DA - 2026/08/30
PB - arXiv
DO - 10.48550/arxiv.2608.29848
UR - https://arxiv.org/abs/2608.29848
AB - We investigate the gravitational form factors (GFFs) of the kaon in a proper-time-regularized three-flavor Nambu--Jona-Lasinio model. We treat the kaon as a light--strange pseudoscalar bound state and evaluate its energy--momentum-tensor matrix element using a dressed quark--graviton vertex. By retaining the interaction-induced contact contribution alongside the quark triangle diagrams, we preserve the gravitational Ward--Takahashi identity and ensure the conservation of the total energy--momentum tensor. We determine the light- and strange-quark contributions to the kaon GFFs, contrast them with the corresponding pion results, and extract the associated pressure and shear-force distributions, together with the Breit-frame and transverse light-front mass radii. Explicit flavor-symmetry breaking dictates that the strange sector carries a larger share of the kaon momentum and mechanical response. Consequently, compared to the pion, the kaon exhibits a less negative D-term and more compact mechanical distributions, featuring enhanced central pressure and shear. We further show that a Ward--Takahashi-identity-preserving reduction of the C-term projection is essential for maintaining the pion low-energy theorem in proper-time regularization.
ER -