Abstract
We perform a matching of the two loop-chiral perturbation theory representation of the scalar Kπ form factor to a dispersive one. Knowing the value of FK/Fπ and f+(0) in the Standard Model (SM) allows to determine two O(p6) LECs, the slope of the scalar form factor and the deviation of the Callan–Treiman theorem. Going beyond the SM and assuming the knowledge of the slope of the scalar form factor from experiment, the matching allows us to determine the ratio of FK/Fπ, f+(0), a certain combination of non-standard couplings, the deviation of the Callan–Treiman theorem and the two O(p6) LECs.
Highlights
One privileged framework for studying meson and baryon properties in the low-energy domain is chiral perturbation theory (ChPT), the effective field theory of the Standard Model (SM)
Physics beyond the Standard Model can lead to a small difference between the axial and vector couplings leading to some small contributions from right-handed currents (RHCs)
We introduced here the Cabibbo angle θneglecting in the SM the ub CKM matrix element as suggested by the measurement of Veuffb
Summary
One privileged framework for studying meson and baryon properties in the low-energy domain is chiral perturbation theory (ChPT), the effective field theory of the Standard Model (SM). We will be concerned with two QCD quantities, the pion and kaon decay constants, Fπ and FK respectively and two of the O(p6) LECs C12 and C34 [2] These last two enter the calculation of two very important quantities, namely the strangeness changing vector and scalar form factors in ChPT at two loops. Going beyond the SM and assuming the knowledge of the slope of the scalar form factor from experiment, the matching will allow us to determine the ratio of FK/Fπ, f+(0), a certain combination of non-standard couplings, the deviation of the Callan-Treiman theorem and the two O(p6) LECs. In section 2, we discuss the decay constants and the vector Kπ form factor.
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