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Ortho-para transition rate in $μ$-molecular hydrogen and the proton's induced pseudoscalar coupling $g_p$

J. H. D. Clark·D. S. Armstrong·T. P. Gorringe·M. D. Hasinoff·P. M. King·T. J. Stocki·S. Tripathi·D. H. Wright·P. A. Zolnierczuk
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Abstract

We report a measurement of the ortho-para transition rate in the p$μ$p molecule. The experiment was conducted at TRIUMF via the measurement of the time dependence of the 5.2 MeV neutrons from muon capture in liquid hydrogen. The measurement yielded an ortho-para rate $Λ_{op} = (11.1 \pm 1.7 \pm^{0.9}_{0.6}) \times 10^4$ s$^{-1}$ that is substantially larger than the earlier result of Bardin {\it et al.} We discuss the striking implications for the proton's induced pseudoscalar coupling $g_p$.

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J. H. D. Clark, D. S. Armstrong, T. P. Gorringe, M. D. Hasinoff, P. M. King, T. J. Stocki, S. Tripathi, D. H. Wright, P. A. Zolnierczuk. 2005-09-19. Ortho-para transition rate in $μ$-molecular hydrogen and the proton's induced pseudoscalar coupling $g_p$. https://doi.org/10.1103/physrevlett.96.073401

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