# Search for psi(2S) -> gamma eta_c(2S) via fully reconstructed eta_c(2S) decays

## TL;DR

This study searched for the decay psi(2S) -> gamma eta_c(2S) using a large dataset but found no evidence of the decay, setting upper limits on the branching fractions for multiple decay modes.

## Contribution

First search for psi(2S) -> gamma eta_c(2S) decay with comprehensive mode analysis and upper limit setting based on a large dataset.

## Key findings

- No signals observed in any decay modes.
- Upper limits set on branching fractions.
- Constraints on eta_c(2S) decay properties.

## Abstract

We report a search for the decay psi(2S) -> gamma eta_c(2S) in a sample of 25.9 million psi(2S) events collected with the CLEO-c detector. No signals are observed in any of the 11 exclusive eta_c(2S) decay modes studied, or in their sum. Product branching fraction upper limits are determined as a function of Gamma[eta_c(2S)] for the 11 individual modes.