@article{arnquist_avignone_barabash_barton_bhimani_blalock_bos_busch_buuck_caldwell_et al._2023, title={Charge trapping correction and energy performance of the MAJORANA DEMONSTRATOR}, volume={107}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.107.045503}, abstractNote={P-type point contact (PPC) high-purity germanium detectors are an important technology in astroparticle and nuclear physics due to their superb energy resolution, low noise, and pulse shape discrimination capabilities. Analysis of data from the MAJORANA DEMONSTRATOR, a neutrinoless double-beta decay experiment deploying PPC detectors enriched in $^{76}$Ge, has led to several novel improvements in the analysis of PPC signals. In this work we discuss charge trapping in PPC detectors and its effect on energy resolution. Small dislocations or impurities in the crystal lattice result in trapping of charge carriers from an ionization event of interest, attenuating the signal and degrading the measured energy. We present a modified digital pole-zero correction to the signal energy estimation that counters the effects of charge trapping and improves the energy resolution of the MAJORANA DEMONSTRATOR by approximately 30% to around 2.4 keV FWHM at 2039 keV, the $^{76}$Ge $Q$-value. An alternative approach achieving similar resolution enhancement is also presented.}, number={4}, journal={PHYSICAL REVIEW C}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bhimani, K. H. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2023}, month={Apr} }
 @article{arnquist_avignone iii_barabash_barton_bhimani_blalock_bos_busch_buuck_caldwell_et al._2023, title={Interpretable boosted-decision-tree analysis for the MAJORANA DEMONSTRATOR}, volume={107}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.107.014321}, abstractNote={The Majorana Demonstrator is a leading experiment searching for neutrinoless double-beta decay with high purity germanium (HPGe) detectors. Machine learning provides a new way to maximize the amount of information provided by these detectors, but the data-driven nature makes it less interpretable compared to traditional analysis. An interpretability study reveals the machine's decision-making logic, allowing us to learn from the machine to feed back to the traditional analysis. In this work, we present the first machine learning analysis of the data from the Majorana Demonstrator; this is also the first interpretable machine learning analysis of any germanium detector experiment. Two gradient boosted decision tree models are trained to learn from the data, and a game-theory-based model interpretability study is conducted to understand the origin of the classification power. By learning from data, this analysis recognizes the correlations among reconstruction parameters to further enhance the background rejection performance. By learning from the machine, this analysis reveals the importance of new background categories to reciprocally benefit the standard Majorana analysis. This model is highly compatible with next-generation germanium detector experiments like LEGEND since it can be simultaneously trained on a large number of detectors.2 MoreReceived 22 July 2022Accepted 15 November 2022DOI:https://doi.org/10.1103/PhysRevC.107.014321©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNeutrinoless double beta decayPhysical SystemsSolid-state detectorsTechniquesMachine learningNuclear PhysicsInterdisciplinary Physics}, number={1}, journal={PHYSICAL REVIEW C}, author={Arnquist, I. J. and Avignone III, F. T. and Barabash, A. S. and Barton, C. J. and Bhimani, K. H. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2023}, month={Jan} }
 @article{arnquist_avignone_barabash_barton_bhimani_blalock_bos_busch_buuck_caldwell_et al._2022, title={Experimental study of C-13(?, n)O-16 reactions in the MAJORANA DEMONSTRATOR calibration data}, volume={105}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.105.064610}, abstractNote={Neutron captures and delayed decays of reaction products are common sources of backgrounds in ultrarare event searches. In this work, we studied C13(α,n)O16 reactions induced by α particles emitted within the calibration sources of the Majorana Demonstrator. These sources are thorium-based calibration standards enclosed in carbon-rich materials. The reaction rate was estimated by using the 6129-keV γ rays emitted from the excited O16 states that are populated when the incoming α particles exceed the reaction Q value. Thanks to the excellent energy performance of the Demonstrator's germanium detectors, these characteristic photons can be clearly observed in the calibration data. Facilitated by Geant4 simulations, a comparison between the observed 6129-keV photon rates and predictions by a talys-based software was performed. The measurements and predictions were found to be consistent, albeit with large statistical uncertainties. This agreement provides support for background projections from (α,n) reactions in future double-beta decay search efforts.3 MoreReceived 2 April 2022Accepted 2 June 2022DOI:https://doi.org/10.1103/PhysRevC.105.064610©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasH & He induced nuclear reactionsNeutrinoless double beta decayNeutron physicsNuclear astrophysicsNuclear reactionsNuclear structure & decaysTransfer reactionsProperties6 ≤ A ≤ 19Nuclear Physics}, number={6}, journal={PHYSICAL REVIEW C}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bhimani, K. H. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2022}, month={Jun} }
 @article{arnquist_avignone_barabash_barton_bhimani_blalock_bos_busch_buuck_caldwell_et al._2022, title={Search for Solar Axions via Axion-Photon Coupling with the MAJORANA DEMONSTRATOR}, volume={129}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.129.081803}, abstractNote={Axions were originally proposed to explain the strong-CP problem in QCD. Through the axion-photon coupling, the Sun could be a major source of axions, which could be measured in solid state detection experiments with enhancements due to coherent Primakoff-Bragg scattering. The Majorana Demonstrator experiment has searched for solar axions with a set of $^{76}$Ge-enriched high purity germanium detectors using a 33 kg-yr exposure collected between Jan. 2017 and Nov. 2019. A temporal-energy analysis gives a new limit on the axion-photon coupling as $g_{a\gamma}<1.45\times 10^{-9}$ GeV$^{-1}$ (95% C.I.) for axions with mass up to 100 eV/$c^2$. This improves laboratory-based limits between about 1 eV/$c^2$ and 100 eV/$c^2$.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Arnquist, I. J. and Avignone, F. T. and Barabash, A. S. and Barton, C. J. and Bhimani, K. H. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2022}, month={Aug} }
 @article{arnquist_avignone_barabash_barton_bhimani_blalock_bos_busch_buuck_caldwell_et al._2022, title={Search for Spontaneous Radiation from Wave Function Collapse in the MAJORANA DEMONSTRATOR}, volume={129}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.129.080401}, abstractNote={The Majorana Demonstrator neutrinoless double-beta decay experiment comprises a 44 kg (30 kg enriched in ^{76}Ge) array of p-type, point-contact germanium detectors. With its unprecedented energy resolution and ultralow backgrounds, Majorana also searches for rare event signatures from beyond standard model physics in the low energy region below 100 keV. In this Letter, we test the continuous spontaneous localization (CSL) model, one of the mathematically well-motivated wave function collapse models aimed at solving the long-standing unresolved quantum mechanical measurement problem. While the CSL predicts the existence of a detectable radiation signature in the x-ray domain, we find no evidence of such radiation in the 19-100 keV range in a 37.5 kg-y enriched germanium exposure collected between December 31, 2015, and November 27, 2019, with the Demonstrator. We explored both the non-mass-proportional (n-m-p) and the mass-proportional (m-p) versions of the CSL with two different assumptions: that only the quasifree electrons can emit the x-ray radiation and that the nucleus can coherently emit an amplified radiation. In all cases, we set the most stringent upper limit to date for the white CSL model on the collapse rate, λ, providing a factor of 40-100 improvement in sensitivity over comparable searches. Our limit is the most stringent for large parts of the allowed parameter space. If the result is interpreted in terms of the Diòsi-Penrose gravitational wave function collapse model, the lower bound with a 95% confidence level is almost an order of magnitude improvement over the previous best limit.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bhimani, K. H. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2022}, month={Aug} }
 @article{arnquist_avignone_barabash_barton_bertrand_blalock_bos_busch_buuck_caldwell_et al._2022, title={Signatures of muonic activation in the MAJORANA DEMONSTRATOR}, volume={105}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.105.014617}, abstractNote={Experiments searching for very rare processes such as neutrinoless double-beta decay require a detailed understanding of all sources of background. Signals from radioactive impurities present in construction and detector materials can be suppressed using a number of well-understood techniques. Background from in-situ cosmogenic interactions can be reduced by siting an experiment deep underground. However, the next generation of such experiments have unprecedented sensitivity goals of 10$^{28}$ years half-life with background rates of 10$^{-5}$cts/(keV kg yr) in the region of interest. To achieve these goals, the remaining cosmogenic background must be well understood. In the work presented here, Majorana Demonstrator data is used to search for decay signatures of meta-stable germanium isotopes. Contributions to the region of interest in energy and time are estimated using simulations, and compared to Demonstrator data. Correlated time-delayed signals are used to identify decay signatures of isotopes produced in the germanium detectors. A good agreement between expected and measured rate is found and different simulation frameworks are used to estimate the uncertainties of the predictions. The simulation campaign is then extended to characterize the background for the LEGEND experiment, a proposed tonne-scale effort searching for neutrinoless double-beta decay in $^{76}$Ge.}, number={1}, journal={PHYSICAL REVIEW C}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bertrand, F. E. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2022}, month={Jan} }
 @article{arnquist_avignone_barabash_barton_bertrand_blalock_bos_busch_buuck_caldwell_et al._2022, title={alpha-event characterization and rejection in point-contact HPGe detectors}, volume={82}, ISSN={["1434-6052"]}, DOI={10.1140/epjc/s10052-022-10161-y}, abstractNote={P-type point contact (PPC) HPGe detectors are a leading technology for rare event searches due to their excellent energy resolution, low thresholds, and multi-site event rejection capabilities. We have characterized a PPC detector's response to α particles incident on the sensitive passivated and p + surfaces, a previously poorly-understood source of background. The detector studied is identical to those in the Majorana Demonstrator experiment, a search for neutrinoless double-beta decay ( 0νββ ) in 76 Ge. α decays on most of the passivated surface exhibit significant energy loss due to charge trapping, with waveforms exhibiting a delayed charge recovery (DCR) signature caused by the slow collection of a fraction of the trapped charge. The DCR is found to be complementary to existing methods of α identification, reliably identifying α background events on the passivated surface of the detector. We demonstrate effective rejection of all surface α events (to within statistical uncertainty) with a loss of only 0.2% of bulk events by combining the DCR discriminator with previously-used methods. The DCR discriminator has been used to reduce the background rate in the 0νββ region of interest window by an order of magnitude in the Majorana Demonstrator and will be used in the upcoming LEGEND-200 experiment.}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL C}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bertrand, F. E. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2022}, month={Mar} }
 @article{arnquist_avignone_barabash_barton_bertrand_blalock_bos_busch_buuck_caldwell_et al._2021, title={Search for double-beta decay of Ge-76 to excited states of Se-76 with the MAJORANA DEMONSTRATOR}, volume={103}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.103.015501}, abstractNote={The majorana demonstrator is a neutrinoless double-β decay search consisting of a low-background modular array of high-purity germanium detectors, ∼2/3 of which are enriched to 88% in Ge76. The experiment is also searching for double-beta decay of Ge76 to excited states (e.s.) in Se76. Ge76 can decay into three daughter states of Se76, with clear event signatures consisting of a ββ-decay followed by the prompt emission of one or two γ rays. This results with high probability in multi-detector coincidences. The granularity of the demonstrator detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9 kg yr of isotopic exposure, the demonstrator has set world leading limits for each e.s. decay of Ge76, with 90% CL lower half-life limits in the range of (0.75–4.0)×1024 yr. In particular, for the 2ν transition to the first 0+ e.s. of Se76, a lower half-life limit of 7.5×1023 yr at 90% CL was achieved.4 MoreReceived 14 August 2020Accepted 2 November 2020DOI:https://doi.org/10.1103/PhysRevC.103.015501©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDouble beta decayNeutrinoless double beta decayProperties59 ≤ A ≤ 89TechniquesRadiation detectorsNuclear Physics}, number={1}, journal={PHYSICAL REVIEW C}, author={Arnquist, I. J. and Avignone, F. T., III and Barabash, A. S. and Barton, C. J. and Bertrand, F. E. and Blalock, E. and Bos, B. and Busch, M. and Buuck, M. and Caldwell, T. S. and et al.}, year={2021}, month={Jan} }