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Dissertation
Calibration of light response for the nEXO neutrinoless double beta decay search with machine learning
Doctor of Philosophy (Ph.D.), Drexel University
Sep 2022
DOI:
https://doi.org/10.17918/00001364
Abstract
Neutrinoless double beta decay (0[nu][beta][beta]) is a rare second-order process that, if observed, would confirm that neutrinos are Majorana fermions. This process violates the conservation of lepton number and hence would provide yet another indication of physics beyond the Standard Model (SM). EXO-200 was an experiment aiming to detect 0[nu][beta][beta], and nEXO is the next generation experiment proposed as a successor to EXO-200 using enriched ¹³⁶Xe in a time projection chamber. It is projected that nEXO will reach a sensitivity of 1.35x10²⁸yr to the 0[nu][beta][beta] half life of ¹³⁶Xe with 10 years of data taking. nEXO uses silicon photomultipliers (SiPMs) for light detection. Calibration of SiPMs is very important to meet the energy resolution requirement of <1% ([sigma]/E) at the 0[nu][beta][beta] Q- Value. This dissertation presents the use of machine learning for scintillation light response function calibration. This method is tested with EXO-200 calibration data from dissolved calibration sources. It is shown that an accurate light response can be constructed with limited calibration data using machine learning. A light calibration framework has been developed, which has been used for different studies related to light calibration for nEXO. Using simulation data from the Geant4 and Chroma simulation packages, it is shown that we can calibrate the nEXO light detectors using alpha decays from ²²²Rn and ²²⁰Rn calibration sources. Using this framework, a detailed study of the spectra of ²³²Th chain and the 0[nu][beta][beta] signal shows that the calibration strategy and light response function algorithm are robust to several SiPM failure scenarios.
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Details
- Title
- Calibration of light response for the nEXO neutrinoless double beta decay search with machine learning
- Creators
- Prakash Gautam
- Contributors
- Michelle Dolinski (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 108 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Physics; Drexel University
- Other Identifier
- 991019104807204721