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Capture rate and neutron helicity asymmetry for ordinary muon capture on hydrogen

Shung-ichi Ando·Fred Myhrer·Kuniharu Kubodera
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Abstract

Applying heavy-baryon chiral perturbation theory to ordinary muon capture (OMC) on a proton, we calculate the capture rate and neutron helicity asymmetry up to next-to-next-to-leading order. For the singlet hyperfine state, we obtain the capture rate Gamma_0 = 695 sec^{-1} while, for the triplet hyperfine state, we obtain the capture rate Gamma_1 = 11.9 sec^{-1} and the neutron asymmetry alpha_1 = 0.93. If the existing formalism is used to relate these atomic capture rates to Gamma_{liq}, the OMC rate in liquid hydrogen, then Gamma_{liq} corresponding to our improved values of Gamma_0 and Gamma_1 is found to be significantly larger than the experimental value, primarily due to the updated larger value of g_A. We argue that this apparent difficulity may be correlated to the specious anomaly recently reported for mu^- + p to n + nu_mu + gamma, and we suggest a possibility to remove these two "problems" simply and simultaneously by reexamining the molecular physics input that underlies the conventional analysis of Gamma_{liq}.

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Shung-ichi Ando, Fred Myhrer, Kuniharu Kubodera. 2001-01-05. Capture rate and neutron helicity asymmetry for ordinary muon capture on hydrogen. https://doi.org/10.1103/physrevc.63.015203

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