Molecular effects in low-energy muon transfer from muonic hydrogen to oxygen

In the present study we determine from the available experimental data the cross section of muon transfer to molecular oxygen at low energies with an account of the oxygen molecule structure. Building on an earlier work, the results highlight the role of the molecular structure effects and significantly improve the agreement with theoretical calculations of the muon transfer rate. An efficient computational model of the kinetics of the processes involving muonic hydrogen atoms in a gaseous mixture of H2 and O2 is developed and analyzed. The model is applied in the description of the FAMU experiment for the measurement of the hyperfine splitting in muonic hydrogen and the Zemach radius of the proton.