Explanation of the seasonal variation of cosmic multiple muon events observed with the NOvA Near Detector

Abstract

The flux of cosmic ray muons at the Earth's surface exhibits seasonal variations due to changes in the temperature of the atmosphere affecting the production and decay of mesons in the upper atmosphere. Using 1473 live days of data collected by the NuMI Off-axis ${\nu }_e$ Appearance (NOvA) Near Detector during 2018--2022, we studied the seasonal pattern in the multiple-muon event rate. The data confirm an anticorrelation between the multiple-muon event rate and effective atmospheric temperature, consistent across all the years of data. Previous analyses from MINOS and NOvA saw a similar anticorrelation but did not include an explanation. We find that this anticorrelation is driven by altitude--geometry effects as the average muon production height changes with the season. This has been studied with a CORSIKA cosmic ray simulation package by varying atmospheric parameters, and provides an explanation to a longstanding discrepancy between the seasonal phases of single and multiple-muon events.

10 pages, 11 figures, 3 tables. Accepted by Phys. Rev. D

References in corpus (6)

• Observation of muon intensity variations by season with the MINOS Near Detector
• Cosmic-muon characterization and annual modulation measurement with Double Chooz detectors
• Observation of seasonal variation of atmospheric multiple-muon events in the MINOS Near and Far Detectors
• Seasonal Variation of the Underground Cosmic Muon Flux Observed at Daya Bay
• Profiles of energetic muons in the atmosphere
• Seasonal Variation of Multiple-Muon Cosmic Ray Air Showers Observed in the NOvA Detector on the Surface