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

•Temperature dependence of the μ transfer rate from μp to oxygen is measured.•A strong monotonic rise by a factor three of the rate is observed between 104-300 K.•This effect will be exploited to measure the hyperfine splitting of the μp 1S state.•Experiment took place at the RIKEN muon facility, Rutherford Appleton Laboratory.•Fast scintillator counters based on LaBr3 crystals read by photomultipliers are used. We report the first measurement of the temperature dependence of muon transfer rate from muonic hydrogen atoms to oxygen between 100 and 300 K. Data were obtained from the X-ray spectra of delayed events in a gaseous target, made of a H2/O2 mixture, exposed to a muon beam. This work sets constraints on theoretical models of muon transfer and is of fundamental importance for the measurement of the hyperfine splitting of muonic hydrogen ground state as proposed by the FAMU collaboration.