Direct WIMP Search with the Dual-Phase Data of the Argon Dark Matter Experiment
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Author
Date
2023Type
- Doctoral Thesis
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Abstract
The Argon Dark Matter (ArDM) experiment is the first tonne-scale dual-phase argon- based direct dark matter detection experiment. It searches for nuclear recoils of ”Weakly interacting massive particles” (WIMPs), a promising dark matter candidate, with the ar- gon nuclei. The recoils produce primary scintillation light signals (S1s) within the liquid phase, and free electrons, which drift towards the gaseous phase inducing the secondary scintillation light signals (S2s) therein. The data reconstruction extracts fundamental char- acteristics of the S1 and S2 signals and matches a number of S2 signals to the original S1 signal. Subsequent data analysis allows the calibration of experimental parameters and the confinement of a region of interest, wherein a particularly high likelihood of nuclear recoils is expected, based on a dedicated neutron calibration data set. In this region of interest the ArDM WIMP search is performed within a fiducial volume of mAr,fid = 574.57 kg and during a measurement period of 8.429 live-days.
The corresponding ArDM exposure of 4’843 kg · days results in an upper exclusion limit on the spin-independent WIMP-nucleon interaction cross section of σSI,p = (2.28 ± 0.02) · 10−41 cm2 for a WIMP candidate of mass mχ = 100 GeV and a minimal upper exclusion limit of σSI,p = (2.16 ± 0.02) · 10−41 cm2 for a WIMP candidate of mass mχ = 120.2 GeV at the 90% confidence level. With the first successful completion of a tonne-scale dual-phase argon-based dark matter experiment ArDM represents a major milestone in the search for dark matter.
This thesis introduces the reader to the history of the search for dark matter and the current status of the field. The theoretical framework of the WIMP interaction in a liquid noble gas detector is explored, and adapted to the presented ArDM detector. The reader is accompanied through the data selection and reconstruction process based on the data collected by ArDM. A detailed overview of the subsequent analysis of the ArDM data is provided with a focus on the discrimination of signal-like nuclear recoils versus a background of electronic recoils, and the estimation of the detector’s resulting efficiency for WIMP- like nuclear recoils. The thesis concludes with a thorough explanation of the statistical procedure involved in setting an upper limit on the expected WIMP signal. The results of the ArDM WIMP search are compared to the current world-leading experimental results, and an out. Show more
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https://doi.org/10.3929/ethz-b-000614359Publication status
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Publisher
ETH ZurichSubject
Dark Matter detectors (WIMPs, axions, etc.)Organisational unit
03503 - Rubbia, André / Rubbia, André
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