Abstract
It has been previously shown that a particular nonperturbative constituent-quark model of hadrons describes experimental measurements of electromagnetic form factors of light charged mesons through a small number of common phenomenological parameters, matching at the same time the Quantum-Chromodynamics (QCD) asymptotics for the pi-meson form factor at large momentum transfer. Here we start with the determination of the K0 electromagnetic form factor in this approach. Precise measurement of the K0 charge radius makes it possible to constrain model parameters with high accuracy. Then, with all parameters fixed, we revisit the K+ form factor and find that it matches experimental measurements in the infrared, lattice results at moderate momentum transfer and the perturbative QCD asymptotics in the ultraviolet. In this way we obtain a narrow constraint on the K+ charge radius, <r_K+^2> = 0.403 +0.007 -0.006 fm^2, and extend the successful infrared-ultraviolet connection from pi to K mesons.
Highlights
AND OUTLINEQuantitative description of strongly coupled composite systems remains one of the principal unsolved problems in particle physics
It has been previously shown that a particular nonperturbative constituent-quark model of hadrons describes experimental measurements of electromagnetic form factors of light charged mesons through a small number of common phenomenological parameters, matching at the same time the quantumchromodynamics (QCD) asymptotics for the π-meson form factor at large momentum transfer
Beyond QCD, the same questions arise in numerous extensions of the Standard Model (SM) of particle physics which predict composite particles bound by new strong gauge forces
Summary
Quantitative description of strongly coupled composite systems remains one of the principal unsolved problems in particle physics. Bound states, even those applicable to particular problems only Predictions obtained within these approaches can be tested on QCD, where experimental results are available. At large Q2, when the constituent-quark masses are switched off, FπðQ2Þ calculated in the model agrees with the perturbative QCD prediction [9,10,11], both in the functional form [12] and numerically [13]. This is remarkable because the correct ultraviolet asymptotics is reached automatically for the same choice of parameters which describes infrared data
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