Measurement of the form-factor ratios for D+ --> K* l nu

TL;DR

This paper reports precise measurements of form-factor ratios in the decay D+ --> K* l nu using Fermilab data, providing new insights into charm semileptonic decays and combining results from muon and electron channels.

Contribution

First measurement of the r3 form factor ratio in D+ --> K* l nu decay, with combined analysis of muon and electron channels for improved accuracy.

Findings

Measured rv=1.87+-0.08+-0.07 for combined channels

Measured r2=0.73+-0.06+-0.08 for combined channels

First measurement of r3=0.04+-0.33+-0.29

Abstract

The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm hadroproduction experiment E791 at Fermilab. From 3034 (595) signal (background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09, r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33 +-0.29. The values of the form factor ratios rv and r2 measured for the muon channel are combined with the values of rv and r2 that we have measured in the electron channel. The combined E791 results for the muon and electron channels are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.