Search for $D^0\to K^-\eta e^+\nu_e$, $D^+\to K_S^0 \eta e^+\nu_e$ and $D^+\to \eta\eta e^+\nu_e$ decays

TL;DR

This study searches for rare semileptonic decays of D mesons using BESIII data, providing first evidence for one decay mode and setting upper limits for others, advancing understanding of charm meson decay processes.

Contribution

First search for specific D meson semileptonic decays, with evidence for $D^0\to K^-\eta e^+\nu_e$ and new upper limits for related decays.

Findings

Evidence for $D^0\to K^-\eta e^+\nu_e$ with 3.3 sigma significance.

Measured branching fraction for $D^0\to K^-\eta e^+\nu_e$ as $(0.84_{-0.34}^{+0.29}\pm0.22)\times 10^{-4}$.

No significant signals for $D^+\to K_S^0 \eta e^+\nu_e$ and $D^+\to \eta\eta e^+\nu_e$, upper limits set.

Abstract

By analyzing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 7.93 fb$^{-1}$, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays $D^0\to K^-\eta e^+\nu_e$, $D^+\to K_S^0 \eta e^+\nu_e$ and $D^+\to \eta\eta e^+\nu_e$ for the first time. We present evidence for $D^0\to K^-\eta e^+\nu_e$ with a significance of $3.3\sigma$. The branching fraction of $D^0\to K^-\eta e^+\nu_e$ is measured to be $(0.84_{-0.34}^{+0.29}\pm0.22)\times 10^{-4}$. Here, the first uncertainties are statistical and the second ones are systematic. No significant signals are observed for the decays $D^+\to K_S^0 \eta e^+\nu_e$ and $D^+\to \eta\eta e^+\nu_e$ and we set the upper limits on their branching fractions.