# Search for the Radiative Leptonic Decay $D^{+}\to \gamma e^{+} {\nu}_{e}$

## TL;DR

This study reports the first search for the rare radiative leptonic decay of the $D^+$ meson into a photon, electron, and neutrino, setting an upper limit on its branching fraction based on BESIII data.

## Contribution

First experimental search for the $D^{+}
ightarrow \gamma e^{+}{
u}_{e}$ decay, providing an upper limit on its branching fraction using BESIII data.

## Key findings

- No significant signal observed for the decay.
- Upper limit on branching fraction set at $3.0\times10^{-5}$ for photon energy > 10 MeV.
- Analysis demonstrates the sensitivity of BESIII to rare charm decays.

## Abstract

Using an electron-positron collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=3.773$ GeV with the BESIII detector, we present the first search for the radiative leptonic decay $D^{+} \rightarrow \gamma e^{+}{\nu}_{e}$. The analysis is performed with a double tag method. We do not observe a significant $D^{+} \rightarrow \gamma e^{+}{\nu}_{e}$ signal, and obtain an upper limit on the branching fraction of $D^{+} \rightarrow \gamma e^{+}{\nu}_{e}$ decay with the energy of radiative photon larger than 10 MeV of $3.0\times10^{-5}$ at the 90% confidence level.