First Observation of Antiproton Annihilation At Rest on Argon in the LArIAT Experiment

TL;DR

This paper presents the first observation and measurement of antiproton annihilation at rest on argon in a liquid argon time projection chamber, providing data to improve nuclear interaction models relevant for particle physics research.

Contribution

It introduces the first experimental detection and detailed analysis of antiproton annihilation on argon, including track multiplicity and particle identification, validated against simulations.

Findings

Mean charged particle tracks from annihilation: 3.2 ± 0.4 (manual), 2.8 ± 0.4 (automated)

Good agreement between data and Monte Carlo simulations

Results align with theoretical predictions for annihilation interactions

Abstract

We report the first observation and measurement of antiproton annihilation at rest on argon using the LArIAT experiment. Antiprotons from a charged particle test beam that come to rest inside LArIAT's liquid argon time projection chamber (LArTPC) are identified through beamline instrumentation and LArTPC track reconstruction algorithms. The multiplicity of charged particle tracks originating from the annihilation vertex is manually assessed through hand-scanning, resulting in a distribution with a mean of 3.2 $\pm$ 0.4 tracks and a standard deviation of 1.3 tracks. This is consistent with an automated track reconstruction, which produces a mean of 2.8 $\pm$ 0.4 tracks and a standard deviation of 1.2 tracks. Good agreement is found between data and Monte Carlo simulations for both methods. Additionally, we report the shower multiplicity and particle identification of outgoing tracks, both of which align closely with theoretical predictions. These findings will contribute to modeling of intranuclear annihilation interactions on argon, including scenarios such as neutron-antineutron oscillations.