Determination of the absolute branching fractions of $D^0\to K^-e^+\nu_e$ and $D^+\to \bar K^0 e^+\nu_e$

TL;DR

This paper measures the absolute branching fractions of specific D meson semileptonic decays using BESIII data, employing a new reconstruction method, and confirms isospin symmetry within uncertainties.

Contribution

It introduces a novel reconstruction technique for measuring D meson decay branching fractions and provides precise measurements consistent with previous results.

Findings

Branching fraction for $D^0 o K^-e^+ u_e$ is (3.567±0.031±0.025)%

Branching fraction for $D^+ o ar K^0 e^+ u_e$ is (8.68±0.14±0.16)%

The ratio of decay partial widths supports isospin symmetry within 1.9σ.

Abstract

Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays $D^0\to K^-e^+\nu_e$ and $D^+\to \bar K^0 e^+\nu_e$ to be $(3.567\pm0.031_{\rm stat}\pm 0.025_{\rm syst})\%$ and $(8.68\pm0.14_{\rm stat}\pm 0.16_{\rm syst})\%$, respectively. Starting with the process $e^+e^-\to D\bar{D}$, a new reconstruction method is employed to select events that contain candidates for both $D\to \bar Ke^+\nu_e$ and $\bar D\to Ke^-\bar \nu_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing $D\to \bar Ke^+\nu_e$ and hadronic $\bar D$ decays. Combining our results with the lifetimes of the $D^0$ and $D^+$ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of $\frac{\bar \Gamma_{D^0\to K^{-}e^+\nu_{e}}}{\bar \Gamma_{D^{+}\to \bar K^{0}e^+\nu_{e}}}=1.039\pm0.021$. This ratio supports isospin symmetry in the $D^0\to K^-e^+\nu_e$ and $D^+\to \bar K^0 e^+\nu_e$ decays within $1.9\sigma$.