Measurements of Pion and Muon Nuclear Capture at Rest on Argon in the LArIAT Experiment

M. A. Hernandez-Morquecho; R. Acciarri; J. Asaadi; M. Backfish; W. Badgett; V. Basque; F. d. M. Blaszczyk; W. Foreman; R. Gomes; E. Gramellini; J. Ho; E. Kearns; E. Kemp; T. Kobilarcik; M. King; B. R. Littlejohn; X. Luo; A. Marchionni; C. A. Moura; J. L. Raaf; D. W. Schmitz; M. Soderberg; J. M. St. John; A. M. Szelc; T. Yang

arXiv · 2408.05133

Measurements of Pion and Muon Nuclear Capture at Rest on Argon in the LArIAT Experiment

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Abstract

We report the measurement of the final-state products of negative pion and muon nuclear capture at rest on argon by the LArIAT experiment at the Fermilab Test Beam Facility. We measure a population of isolated MeV-scale energy depositions, or blips, in 296 LArIAT events containing tracks from stopping low-momentum pions and muons. The average numbers of visible blips are measured to be 0.74 $\pm$ 0.19 and 1.86 $\pm$ 0.17 near muon and pion track endpoints, respectively. The 3.6$\sigma$ statistically significant difference in blip content between muons and pions provides the first demonstration of a new method of pion-muon discrimination in neutrino liquid argon time projection chamber experiments. LArIAT Monte Carlo simulations predict substantially higher average blip counts for negative muon (1.22 $\pm$ 0.08) and pion (2.34 $\pm$ 0.09) nuclear captures. We attribute this difference to Geant4's inaccurate simulation of the nuclear capture process.

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M. A. Hernandez-Morquecho, R. Acciarri, J. Asaadi, M. Backfish, W. Badgett, V. Basque, F. d. M. Blaszczyk, W. Foreman, R. Gomes, E. Gramellini, J. Ho, E. Kearns, E. Kemp, T. Kobilarcik, M. King, B. R. Littlejohn, X. Luo, A. Marchionni, C. A. Moura, J. L. Raaf, D. W. Schmitz, M. Soderberg, J. M. St. John, A. M. Szelc, T. Yang. 2024-08-09. Measurements of Pion and Muon Nuclear Capture at Rest on Argon in the LArIAT Experiment. https://arxiv.org/abs/2408.05133

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