Measurement of D0 -> pilnu (Klnu) and their form factors

TL;DR

This study measures the branching fractions and form factor ratios of D0 meson semileptonic decays to pions and kaons using a novel reconstruction method with data from the Belle experiment.

Contribution

It introduces a new global reconstruction technique that improves neutrino momentum resolution and provides precise measurements of decay ratios and form factors.

Findings

Measured branching fraction ratios with statistical and systematic uncertainties.

Determined the semileptonic form factor ratio at q^2=0.

Demonstrated the effectiveness of the novel reconstruction method.

Abstract

Using a data sample of 282 1/fb collected by the Belle experiment at the KEKB e+e- collider, we study D0 -> pilnu and D0 -> Klnu decays (l = mu,e) in e+e- annihilation. We identify D* -> D0pi decays by using the mass of the system recoiling against a fully reconstructed tag-side D* or D meson, allowing for additional primary mesons from fragmentation. Using a novel global reconstruction method that provides very good resolution in neutrino momentum and in q^2 = (p_l+p_nu)^2, we reconstructed D0 -> pilnu and D0 -> Klnu decays. From these events we measured the branching fraction ratios BR(D0 -> pienu)/BR(D0 -> Kenu) = 0.0809 +- 0.0080 +- 0.0032$ and BR(D0 -> pimunu)/BR(D0 -> Kmunu) = 0.0677 +- 0.0078 +- 0.0047, and the semileptonic form factor ratio f+(D0 -> pilnu})^2/f+(D0 -> Klnu})^2|Vcd|^2/|Vcs|^2|_{q^2=0} = 0.041 +- 0.003 +- 0.004, where the errors are statistical and systematic, respectively.