Measurement of the cosmic muon annual and diurnal flux variation with the COSINE-100 detector

Abstract

We report measurements of annual and diurnal modulations of the cosmic-ray muon rate in the Yangyang underground laboratory (Y2L) using 952 days of COSINE-100 data acquired between September 2016 and July 2019. A correlation of the muon rate with the atmospheric temperature is observed and its amplitude on the muon rate is determined. The effective atmospheric temperature and muon rate variations are positively correlated with a measured effective temperature coefficient of α T = 0.80 ± 0.11. This result is consistent with a model of meson production in the atmosphere. We also searched for a diurnal modulation in the underground muon rate by comparing one-hour intervals. No significant diurnal modulation of the muon rate was observed.

Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target

“…An event satisfying the trigger condition of coincident photoelectrons in both of the crystal’s readout PMTs within 200 ns is acquired with 500-MHz flash analog-to-digital converters and is recorded as an 8-μs-long waveform starting 2.4 μs before occurrence of the trigger ( 30 ). In the offline analysis, muon-induced events are rejected when the crystal hit event occurs within 30 ms after a muon candidate event in the muon detector ( 29 , 42 ). In addition, we require that leading edges of the trigger pulses start later than 2.0 μs after the start of the recording, waveforms from the crystal contain more than two single photoelectrons, and the integral waveform area below the baseline does not exceed a limit.…”

Searching for low-mass dark matter via Migdal effect in COSINE-100

“…The LAB-LS is contained within a box made with 1 cm thick acrylic and 3 cm thick oxygen-free copper that is surrounded by a 20 cm thick lead shield. An outer array of plastic scintillation counters is used to tag and veto cosmic-ray muons [29,33].…”

Three-year annual modulation search with COSINE-100

“…External backgrounds are further reduced by a shielding structure composed of a layer of 3-cm thick copper surrounded by 20 cm of lead. Thirty-seven 3-cm thick plastic scintillator panels placed around the shielding structure provide 4π cosmic ray muon tagging [20,21].…”