Measurement of the Formation Rate of Muonic Hydrogen Molecules

Abstract

Background: The rate λ_ppμ characterizes the formation of ppμ molecules in collisions of muonic pμ atoms with hydrogen. In measurements of the basic weak muon capture reaction on the proton to determine the pseudoscalar coupling g_P, capture occurs from both atomic and molecular states. Thus knowledge of λ_ppμ is required for a correct interpretation of these experiments. Purpose: Recently the MuCap experiment has measured the capture rate Λ_S from the singlet pμ atom, employing a low density active target to suppress ppμ formation (PRL 110, 12504 (2013)). Nevertheless, given the unprecedented precision of this experiment, the existing experimental knowledge in λ_ppμ had to be improved. Method: The MuCap experiment derived the weak capture rate from the muon disappearance rate in ultra-pure hydrogen. By doping the hydrogen with 20 ppm of argon, a competing process to ppμ formation was introduced, which allowed the extraction of λ_ppμ from the observed time distribution of decay electrons. Results: The ppμ formation rate was measured as λ_ppμ= (2.01 +- 0.06(stat) +- 0.03(sys)) 10^6 s^-1. This result updates the λ_ppμ value used in the above mentioned MuCap publication. Conclusions: The 2.5x higher precision compared to earlier experiments and the fact that the measurement was performed at nearly identical conditions to the main data taking, reduces the uncertainty induced by λ_ppμ to a minor contribution to the overall uncertainty of Λ_S and g_P, as determined in MuCap. Our final value for λ_ppμ shifts Λ_S and g_P by less than one tenth of their respective uncertainties compared to our results published earlier.

arXiv comment12 pages, 6 figures, to be submitted to Phys. Rev. C

References in corpus (13)

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• Induced pseudoscalar coupling of the proton weak interaction
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• Electroweak Radiative Corrections to Muon Capture
• A Circulating Hydrogen Ultra-High Purification System for the MuCap Experiment
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• Diffusion radius of muonic hydrogen atoms in H-D gas
• A high-pressure hydrogen time projection chamber for the MuCap experiment
• An update of muon capture on hydrogen

Cited by in corpus (12)

• Axial Vector Form Factors of the Nucleon from Lattice QCD
• Axial Vector Form Factors from Lattice QCD that Satisfy the PCAC Relation
• Precision Nucleon Charges and Form Factors Using 2+1-flavor Lattice QCD
• Nucleon Axial Radius and Muonic Hydrogen - A New Analysis and Review
• Iso-vector axial form factors of the nucleon in two-flavour lattice QCD
• Nucleon axial-vector and pseudoscalar form factors, and PCAC relations
• Contact interaction analysis of octet baryon axialvector and pseudoscalar form factors
• Question of Lorentz invariance in muon decay
• Axial and pseudoscalar form factors from charged current quasielastic neutrino-nucleon scattering
• First measurement of the temperature dependence of muon transfer rate from muonic hydrogen atoms to oxygen
• FAMU: study of the energy dependent transfer rate ${\Lambda }_{\mu p\to \mu O}$
• An influence of the spectator-nuclear motion on nonresonant formation of the muonic hydrogen molecules