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Observation of double radiative capture on pionic hydrogen

S. Tripathi·D. S. Armstrong·M. E. Christy·J. H. D. Clark·T. P. Gorringe·M. D. Hasinoff·M. A. Kovash·D. H. Wright·P. A. Zolnierczuk
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Abstract

We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer, and detected $γ$--ray coincidences following $π^-$ stops in liquid hydrogen. We found the branching ratio for double radiative capture to be $(3.05 \pm 0.27(stat.) \pm 0.31(syst.)) \times 10^{-5}$. The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the $ππ\to γγ$ annihilation mechanism.

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S. Tripathi, D. S. Armstrong, M. E. Christy, J. H. D. Clark, T. P. Gorringe, M. D. Hasinoff, M. A. Kovash, D. H. Wright, P. A. Zolnierczuk. 2002-10-26. Observation of double radiative capture on pionic hydrogen. https://doi.org/10.1103/physrevlett.89.252501

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