Muon detector for the COSINE-100 experiment

Abstract

The COSINE-100 dark matter search experiment has started taking physics data with the goal of performing an independent measurement of the annual modulation signal observed by DAMA/LIBRA. A muon detector was constructed by using plastic scintillator panels in the outermost layer of the shield surrounding the COSINE-100 detector. It is used to detect cosmic ray muons in order to understand the impact of the muon annual modulation on dark matter analysis. Assembly and initial performance test of each module have been performed at a ground laboratory. The installation of the detector in Yangyang Underground Laboratory (Y2L) was completed in the summer of 2016. Using three months of data, the muon underground flux was measured to be 328 ± 1(stat.)± 10(syst.) muons/m 2 /day. In this report, the assembly of the muon detector and the results from the analysis are presented.

Initial performance of the COSINE-100 experiment

“…± 0.12(syst.) × 10 −7 cm −2 s −1 [37] while the flux in A6 is 2.7 × 10 −7 cm −2 s −1 [38]. Experimental rooms are built in the caverns located at the mid-sections of the tunnels.…”

“…cosmic-ray muon flux at the COSINE-100 detector was measured to be 328±1(stat.)±10(syst.) muons/m 2 /day [37]. The current NaI(Tl) crystal event selection requires a coincidence within a 30 ms time window between a crystal triggered event and a muon panel event to select the muon induced events.…”

Neutron and muon-induced background studies for the AMoRE double-beta decay experiment

“…Therefore, the integrated muon intensity (through a horizontal area) at YEMI can be normalized by the measured flux. The total muon flux at YEMI is thus considered as 8.2×10 −8 muons/cm 2 /s, which is derived by using the flux of 328±1(stat)±10(syst) muons/m 2 /day, measured at the Yangyang underground laboratory (Y2L) [14] by the COSINE-100 experiment [15]. YEMI is located ∼1.5 times deeper than Y2L and, thus, the integrated muon intensities in the units of muons/cm 2 /s for two sites, calculated from Eqs.…”

Search for a Dark Matter-Induced Annual Modulation Signal in NaI(Tl) with the COSINE-100 Experiment

“…C1, C5, and C8 are excluded from this analysis due to their high background (about twice that of the other crystals), high noise rate (C1), and low light yield (C5 and C8), for a total effective mass of 61.3 kg. The detector is surrounded by passive and active shielding that includes, from the inside out, copper plates of 3 cm in total thickness, 20 cm of lead, and 3 cm of 37 plastic scintillator panels for cosmic ray muon tagging [30]. More details of the experimental apparatus are presented in Ref.…”

“…The humidity inside the shielding structure is kept at < 5% RH and the high heat capacity helps to keep the temperature within the liquid stable at 24.2±0.1 • C. The radon level in the detector room is measured at 36±10 Bq/m 3 . The time dependence of temperature, humidity, radon, and cosmic ray muons [30] is shown in Fig. 1.…”