Orbital angular momentum in the pion and kaon: Rest-frame and light-front
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Doi 10.1016/j.physletb.2026.140361
Volumen 876
2026-05-01
Citas: 0
Copyright © 2026. Published by Elsevier B.V.Orbital angular momentum (OAM) is not a Poincaré invariant quantity; so, its value is observer dependent. Notwithstanding that, in quantum chromodynamics, a Poincaré-invariant theory, OAM is part of every hadron wave function. Using continuum Schwinger function methods, we elucidate both the subjective character of in-hadron OAM and expose some of its impacts on pion and kaon structure and observables. For instance, working with light-front projections of their Bethe-Salpeter wave functions, it is found that the pion is a roughly 50/50 mix of light-front OAM zero and one components and the kaon is a 60/40 system. The overall picture is that (near) Nambu-Goldstone modes are complex bound states, each with significant intrinsic OAM, independent of the observer’s reference frame. This feature must be accounted for in the calculation of observables. Inductively, the same is true for all hadrons.
Dyson-Schwinger equations, Light-front wave functions, Orbital angular momentum, Pion and kaon structure, Poincaré covariance, Quantum chromodynamics
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