# First measurement of the temperature dependence of muon transfer rate from muonic hydrogen atoms to oxygen

## TL;DR

This study measures how the rate of muon transfer from muonic hydrogen to oxygen varies with temperature between 100 and 300 K, revealing an unexpected increase at low energies.

## Contribution

It provides the first experimental data on the temperature dependence of muon transfer rates, challenging existing constant-rate models.

## Key findings

- Muon transfer rate increases 8-fold from 100 to 300 K.
- Data constrains theoretical models of muon transfer.
- Results are crucial for hyperfine splitting measurements of muonic hydrogen.

## Abstract

We report the first measurement of the temperature dependence of muon transfer rate from $\mu$p atoms to oxygen between 100 and 300 K. Data were obtained from the X-ray spectra of delayed events in gaseous target H$_2$/O$_2$ exposed to a muon beam. Based on the data, we determined the muon transfer energy dependence up to 0.1 eV, showing an 8-fold increase in contrast with the predictions of constant rate in the low energy limit. This work set constraints on theoretical models of muon transfer, and is of fundamental importance for the measurement of the hyperfine splitting of $\mu$p by the FAMU collaboration.