Measurement of the absolute branching ratios for semileptonic K+/- decays with the KLOE detector

TL;DR

This paper reports precise measurements of the absolute branching ratios for charged kaon semileptonic decays using a large dataset from the KLOE detector, providing key inputs for testing the Standard Model and extracting the CKM matrix element V_{us}.

Contribution

The study provides the first precise absolute measurements of K+/- -> p0 e nu and K+/- -> p0 mu nu branching ratios with radiation included, and derives related parameters like V_{us}f_{+}(0).

Findings

BR(Ke3) = 0.04965 +/- 0.00038 (stat) +/- 0.00037 (syst)

BR(Kmu3) = 0.03233 +/- 0.00029 (stat) +/- 0.00026 (syst)

Kmu3/Ke3 ratio = 0.6511 +/- 0.0064

Abstract

Using a sample of over 600 million phi->K+K- decays collected at the Dafne e+e- collider, we have measured with the KLOE detector the absolute branching ratios for the charged kaon semileptonic decays, K+/- -> p0 e nu (gamma) (Ke3) and K+/- -> p0 mu nu (gamma) (Kmu3). The results, BR(Ke3) = 0.04965 +/- 0.00038_{stat} +/- 0.00037_{syst} and BR(Kmu3) = 0.03233 +/- 0.00029_{stat} +/- 0.00026_{syst}, are inclusive of radiation. Accounting for correlations, we derive the ratio Kmu3/Ke3 = 0.6511+/-0.0064. Using the semileptonic form factors measured in the same experiment, we obtain V_{us}f_{+}(0) = 0.2141 +/- 0.0013.