# Long-lived $2s$ state of muonic hydrogen: population and lifetime - Nuclear Theory

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Abstract: Ab initio study of the density-dependent population and lifetime of thelong-lived $\mu p {2s}$ and the yield of $\mu p {1s}$ atoms with kineticenergy 0.9 keV have been performed for the first time. The direct Coulomb$2s\to 1s$ deexcitation is proved to be the dominant quenching mechanism of the$2s$ state at kinetic energy below $2p$ threshold and explain the lifetime ofthe metastable $2s$ state and high-energy 0.9 keV component of $\mu p {1S}$observed at low densities. The cross sections of the elastic, Stark and Coulombdeexcitation processes have been calculated in the close-coupling approachtaking into account for the first time both the closed channels and thethreshold effects due to vacuum polarization shifts of the $ns$ states. Thecross sections are used as the input data in the detailed study of the atomiccascade kinetics. The theoretical predictions are compared with the knownexperimental data at low densities. The 40% yield of the 0.9 keV$\mu p {1s}$atoms is predicted for liquid hydrogen density.

Author: V.P. Popov, V.N. Pomerantsev

Source: https://arxiv.org/