Constraining the properties of K_{l3} form factors with analyticity and unitarity

TL;DR

This paper uses a model-independent approach combining unitarity bounds, pQCD, chiral symmetry, and experimental data to constrain the shape parameters of K_{l3} form factors, excluding certain zero regions.

Contribution

It introduces a novel framework that integrates multiple theoretical and experimental inputs to tightly constrain K_{l3} form factors without relying on specific models.

Findings

Boundaries on scalar and vector form factor parameters established.

Regions with possible zeros on the real and complex energy planes are excluded.

Scalar form factor at a specific kinematic point is precisely constrained.

Abstract

Bounds on the shape parameters of K_{l3} form factors are investigated in a general model independent framework. Using the method of unitarity bounds for correlators evaluated in pQCD, chiral symmetry and experimental information on the phase and modulus of \pi K form factors up to an energy t_{in}=1 GeV^2, we constrain the shape parameters of the scalar and vector form factors, the value of the scalar form factor at t=M_\pi^2-M_K^2, and exclude regions where zeros can exist on the real energy line and in the complex energy plane.