High statistic measurement of the K- -> pi0 e- nu decay form-factors

TL;DR

This study provides a high-statistics measurement of the decay form-factors in K- -> pi0 e- nu decays, offering precise parameters and limits on non-standard couplings, advancing understanding of kaon semileptonic decay dynamics.

Contribution

The paper presents the most precise measurement of the decay form-factors and limits on tensor and scalar couplings in K- -> pi0 e- nu decays using a large dataset.

Findings

Measured the linear slope parameter lambda+ with high precision.

Estimated the quadratic contribution to the form-factor.

Derived limits on tensor and scalar couplings.

Abstract

The decay K- -> pi0 e- nu is studied using in-flight decays detected with the ISTRA+ spectrometer. About 920K events are collected for the analysis. The lambda+ slope parameter of the decay form-factor f+(t) in the linear approximation (average slope) is measured: lambda+(lin)= 0.02774 +- 0.00047(stat) +- 0.00032(syst). The quadratic contribution to the form-factor was estimated to be lambda'+ = 0.00084 +- 0.00027(stat) +- 0.00031(syst). The linear slope, which has a meaning of df+(t)/dt|_{t=0} for this fit, is lambda+ = 0.02324 +- 0.00152(stat) +- 0.00032(syst). The limits on possible tensor and scalar couplings are derived: f_{T}/f_{+}(0)=-0.012 +- 0.021(stat) +- 0.011$(syst), f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).