Abstract
Clean tests of a small admixture of right-handed quark currents directly coupled to the standard W are still lacking. We show that such non-standard couplings can be significantly constrained measuring the value of the scalar Kpi form factor at the Callan-Treiman point to a few percent. A realistic prospect of such a measurement in K^L_{mu3} decay based on an accurate dispersive representation of the scalar form factor is presented. The inadequacy of the currently used linear parametrisation is explained and illustrated using recent KTeV data. We briefly comment on the charged Kaon mode.
Highlights
Clean tests of a small admixture of right-handed quark currents directly coupled to the standard W are still lacking
We show how high statistics measurements [1, 2] of Dalitz distributions in the KμL3 decay, KL → π±μ∓ν, can be used to extract the value C = f (∆Kπ) of the scalar Kπ form factor at the Callan-Treiman point ∆Kπ = m2K0 − m2π+ and how this information constrains the effect of ud and us right-handed currents (RHCs)
It is based on the observation that standard dispersive technics and the known low-energy Kπ phases lead to an accurate parametrization of the scalar Kπ form factor in terms of a single parameter C subject to experimental determination
Summary
Whereas the weighted average of the 3 compatible most recent measurements of the inclusive decay rate KeL3(γ) by KTeV [23], NA48 [24], and KLOE [25] leads to. The expression for C can be rewritten as:. Is precisely known from superallowed 0+ → 0+ nuclear β-decays [26] with the recently updated accuracy [27]. Is Bexp = 1.2418 ± 0.0043 using Eqs. The parameter r is given by the RHCs effective couplings r=
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