# Theory of rare charm decays into leptons

## TL;DR

This paper reviews the theoretical aspects of rare charm meson decays into leptons, emphasizing the potential of heavy quarkonium transitions to detect lepton-flavor violation more effectively than $D$ meson decays.

## Contribution

It highlights the importance of heavy quarkonium transitions as a promising avenue for studying lepton-flavor violation in charm decays, offering insights beyond traditional $D$ meson analyses.

## Key findings

- Heavy quarkonium transitions can provide more sensitive tests for LFV.
- Rare charm decays are valuable probes for new physics beyond the Standard Model.
- Theoretical implications guide future experimental searches for LFV.

## Abstract

Studies of rare decays of charmed mesons into the final states containing leptons is an important vehicle in low-energy searches for new physics. I review theoretical implications of those studies involving transitions with and without lepton flavor conservation. I argue that lepton-flavor violation (LFV) could be successfully studied in heavy quarkonium transitions yielding more sensitive results than similar searches involving $D$ mesons.