μ-capture and ortho-para transitions in the muonic molecule ppμ

The capture of a muon by protons at different hydrogen densities is considered. More precise values of γ-factors for ortho- and para-states of the muonic molecule ppμ are obtained: 2γ_o = 1.009±0.001 and 2γ_p = 1.143±0.001. Relativistic effects are taken into account in the muonic molecule, and the rate of ortho-para transitions λ_op = (7.1±1.2) × 10⁴s^?1, caused by these effects, is calculated. With this value of λ_op the μ-capture rate in liquid hydrogen is found to be Λ_c = (490±10)s^?1 that is in agreement with the value Λ_c = 460±20 s^? recently measured by the Saclay-CERN-Bologna collaboration.