Search

We use data from the COHERENT CsI[Na] scintillation detector to constrain sub-GeV leptophobic dark matter models. This detector was built to observe low-energy nuclear recoils from coherent elastic neutrino-nucleus scattering. These capabilities enable searches for dark matter particles produced at the Spallation Neutron Source mediated by a vector portal particle with masses between 2 and 400 MeV/c2. No evidence for dark matter is observed and a limit on the mediator coupling to quarks is placed. This constraint improves upon previous results by two orders of magnitude. This newly explored parameter space probes the region where the dark matter relic abundance is explained by leptophobic dark matter when the mediator mass is roughly twice the dark matter mass. COHERENT sets the best constraint on leptophobic dark matter at these masses.

Imperfections in analog-to-digital conversion (ADC) cannot be ignored when signal digitization requirements demand both wide dynamic range and high resolution, as is the case for the Majorana Demonstrator 76Ge neutrinoless double-beta decay search. Enabling the experiment’s high-resolution spectral analysis and efficient pulse shape discrimination required careful measurement and correction of ADC nonlinearities. A simple measurement protocol was developed that did not require sophisticated equipment or lengthy data-taking campaigns. A slope-dependent hysteresis was observed and characterized. A correction applied to digitized waveforms prior to signal processing reduced the differential and integral nonlinearities by an order of magnitude, eliminating these as dominant contributions to the systematic energy uncertainty at the double-beta decay $Q$ value.

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.

The structure of nuclei around the neutron-rich nucleus 132Sn is of particular interest due to the vicinity of the Z = 50 and N = 82 shell closures and the r-process nucleosynthetic path. Four states in 131Sn with a strong single-particle-like component have previously been studied via the (d,p) reaction, with limited excitation energy resolution. The 130Sn(9Be,8Be)131Sn and 130Sn(13C,12C)131Sn single-neutron transfer reactions were performed in inverse kinematics at the Holifield Radioactive Ion Beam Facility using particle-gamma coincidence spectroscopy. The uncertainties in the energies of the single-particle-like states have been reduced by more than an order of magnitude using the energies of gamma rays. The previous tentative Jpi values have been confirmed. Decays from high-spin states in 131Sn have been observed following transfer on the isomeric component of the 130Sn beam. The improved energies and confirmed spin-parities of the p-wave states important to the r-process lead to direct-semidirect cross-sections for neutron capture on the ground state of 130Sn at 30 keV that are in agreement with previous analyses. A similar assessment of the impact of neutron-transfer on the isomer would require significant nuclear structure and reaction theory input. There are few measurements of transfer reaction on isomers, and this is the first on an isomer in the 132Sn region., Comment: 7 pages, 4 figures

If dark matter has mass lower than around 1 GeV, it will not impart enough energy to cause detectable nuclear recoils in many direct-detection experiments. However, if dark matter is upscattered to high energy by collisions with cosmic rays, it may be detectable in both direct-detection experiments and neutrino experiments. We report the results of a dedicated search for boosted dark matter upscattered by cosmic rays using the PROSPECT reactor antineutrino experiment. We show that such a flux of upscattered dark matter would display characteristic diurnal sidereal modulation, and use this to set new experimental constraints on sub-GeV dark matter exhibiting large interaction cross-sections., 11 pages, 8 figures

Author(s): Arnquist, IJ; Avignone, FT; Barabash, AS; Barton, CJ; Bertrand, FE; Blalock, E; Bos, B; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Clark, ML; Cuesta, C; Detwiler, JA; Drobizhev, A; Edwards, TR; Edwins, DW; Efremenko, Y; Ejiri, H; Elliott, SR; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Haufe, CR; Henning, R; Hervas Aguilar, D; Hoppe, EW; Hostiuc, A; Kidd, MF; Kim, I; Kouzes, RT; Lopez, AM; Lopez-Castano, JM; Martin, EL; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; Oli, TK; Othman, G; Paudel, LS; Pettus, W; Poon, AWP; Radford, DC; Reine, AL; Rielage, K; Ruof, NW; Saykl, B; Stortini, MJ; Tedeschi, D; Varner, RL; Vasilyev, S; Wilkerson, JF; Wiseman, C; Xu, W; Yu, CH; Zhu, BX | Abstract: 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.

We report on the technical design and expected performance of a 592 kg heavy-water-Cherenkov detector to measure the absolute neutrino flux from the pion-decay-at-rest neutrino source at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The detector will be located roughly 20 m from the SNS target and will measure the neutrino flux with better than 5% statistical uncertainty in 2 years. This heavy-water detector will serve as the first module of a two-module detector system to ultimately measure the neutrino flux to 2-3% at both the First Target Station and the planned Second Target Station of the SNS. This detector will significantly reduce a dominant systematic uncertainty for neutrino cross-section measurements at the SNS, increasing the sensitivity of searches for new physics., Comment: As accepted to JINST

The precision reactor oscillation and spectrum experiment, PROSPECT, has made world-leading measurements of reactor antineutrinos at short baselines. In its first phase, conducted at the high flux isotope reactor (HFIR) at Oak Ridge National Laboratory, PROSPECT produced some of the strongest limits on eV-scale sterile neutrinos, made a precision measurement of the reactor antineutrino spectrum from 235U, and demonstrated the observation of reactor antineutrinos in an aboveground detector with good energy resolution and well-controlled backgrounds. The PROSPECT collaboration is now preparing an upgraded detector, PROSPECT-II, to probe yet unexplored parameter space for sterile neutrinos and contribute to a full resolution of the reactor antineutrino anomaly, a longstanding puzzle in neutrino physics. By pressing forward on the world’s most precise measurement of the 235U antineutrino spectrum and measuring the absolute flux of antineutrinos from 235U, PROSPECT-II will sharpen a tool with potential value for basic neutrino science, nuclear data validation, and nuclear security applications. Following a two-year deployment at HFIR, an additional PROSPECT-II deployment at a low enriched uranium reactor could make complementary measurements of the neutrino yield from other fission isotopes. PROSPECT-II provides a unique opportunity to continue the study of reactor antineutrinos at short baselines, taking advantage of demonstrated elements of the original PROSPECT design and close access to a highly enriched uranium reactor core.

Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of [Formula: see text] is important when making theoretical predictions. One source of [Formula: see text] that is often neglected arises from the irradiation of the nonfuel materials in reactors. The [Formula: see text] rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible [Formula: see text] sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the [Formula: see text] source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel [Formula: see text] contributions from HFIR to PROSPECT amount to 1% above the inverse beta decay threshold with a maximum contribution of 9% in the 1.8–2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel [Formula: see text] contribution.

Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of ν ¯ e is important when making theoretical predictions. One source of ν ¯ e that is often neglected arises from the irradiation of the nonfuel materials in reactors. The ν ¯ e rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible ν ¯ e sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the ν ¯ e source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel ν ¯ e contributions from HFIR to PROSPECT amount to 1% above the inverse beta decay threshold with a maximum contribution of 9% in the 1.8-2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel ν ¯ e contribution.

We report the first measurement of coherent elastic neutrino-nucleus scattering (\cevns) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two independent analyses prefer \cevns over the background-only null hypothesis with greater than $3\sigma$ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2 $\pm$ 0.7) $\times$10$^{-39}$ cm$^2$ -- consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the \cevns process and provides improved constraints on non-standard neutrino interactions., Comment: 8 pages, 5 figures with 2 pages, 6 figures supplementary material V3: fixes to figs 3,4 V4: fix typo in table 1, V5: replaced missing appendix, V6: fix Eq 1, new fig 3, V7 final version, updated with final revisions

Radioactive ^{129}Sb, which can be treated as a proton plus semimagic ^{128}Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, B(E2), for the 2^{+}⊗πg_{7/2} multiplet members and candidate πd_{5/2} state were measured. The results indicate that the total electric quadrupole strength of ^{129}Sb is a factor of 1.39(11) larger than the ^{128}Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wave functions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure.

The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decays in germanium-76 and to demonstrate the feasibility to deploy a ton-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and $^{76}\textrm{Ge}$-enriched germanium detectors totaling 44.1 kg (29.7 kg enriched detectors), located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Data taken with this setup since summer 2015 at different construction stages of the experiment show a clear reduction of the observed background index around the ROI for $0\nu\beta\beta$-decay search due to improvements in shielding. We discuss the statistical approaches to search for a $0\nu\beta\beta$-signal and derive the physics sensitivity for an expected exposure of $10\,\textrm{kg}{\cdot}\textrm{y}$ from enriched detectors using a profile likelihood based hypothesis test in combination with toy Monte Carlo data., Comment: 5 page, 2 figures, to appear in Proceedings of TAUP 2017 - XV International Conference on Topics in Astroparticle and Underground Physics, 24 - 28 July 2017, Sudbury, ON, Canada

The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decays in germanium-76 and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and $^{76}$Ge-enriched germanium detectors totalling 44.1 kg, located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Any neutrinoless double-beta decay search requires a thorough understanding of the background and the signal energy spectra. The various techniques employed to ensure the integrity of the measured spectra are discussed. Data collection is monitored with a thorough set of checks, and subsequent careful analysis is performed to qualify the data for higher level physics analysis. Instrumental background events are tagged for removal, and problematic channels are removed from consideration as necessary., Comment: 5 pages, 2 figures, Proceedings of TAUP 2017 - XV International Conference on Topics in Astroparticle and Underground Physics (Sudbury ON, Canada, July 24-28, 2017)

We report on the preparation of and calibration measurements with a $^{83\mathrm{m}}$Kr source for the CENNS-10 liquid argon detector. $^{83\mathrm{m}}$Kr atoms generated in the decay of a $^{83}$Rb source were introduced into the detector via injection into the Ar circulation loop. Scintillation light arising from the 9.4 keV and 32.1 keV conversion electrons in the decay of $^{83\mathrm{m}}$Kr in the detector volume were then observed. This calibration source allows the characterization of the low-energy response of the CENNS-10 detector and is applicable to other low-energy-threshold detectors. The energy resolution of the detector was measured to be 9$\%$ at the total $^{83\mathrm{m}}$Kr decay energy of 41.5 keV. We performed an analysis to separately calibrate the detector using the two conversion electrons at 9.4 keV and 32.1 keV, Comment: v2: As accepted to JINST

Neutrinoless double-beta decay searches seek to determine the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The {\sc Majorana} Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in $^{76}$Ge. The {\sc Majorana Demonstrator} is composed of 44.8~kg (29.7 kg enriched in $^{76}$Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals of the {\sc Demonstrator} are to establish the required background and scalability of a Ge-based, next-generation, tonne-scale experiment. Following a commissioning run that began in 2015, the first detector module started physics data production in early 2016. We will discuss initial results of the Module 1 commissioning and first physics run, as well as the status and potential physics reach of the full {\sc Majorana Demonstrator} experiment. The collaboration plans to complete the assembly of the second detector module by mid-2016 to begin full data production with the entire array., Neutrino 2016 proceeding

The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultralow background, 40-kg modular high purity Ge (HPGe) detector array to search for neutrinoless double-beta decay (0νββ-decay) in 76Ge. The goal of the experiment is to demonstrate a background rate at or below 3 counts/(t-y) in the 4 keV region of interest (ROI) around the 2039 keV Q-value for 76Ge 0νββ-decay. In this paper, the status of the MAJORANA DEMONSTRATOR, including its design and measurements of properties of the HPGe crystals is presented.

GODDESS is a coupling of the charged-particle detection system ORRUBA to the gamma-ray detector array Gammasphere. This coupling has been developed in order to facilitate the high-resolution measurement of direct reactions in normal and inverse kinematics with stable and radioactive beams. GODDESS has been commissioned using a beam of 134 Xe at 10 MeV/A, in a campaign of stable beam measurements. The measurement demonstrates the capabilities of GODDESS under radioactive beam conditions, and provides the first data on the single-neutron states in 135 Xe, including previously unobserved states based on the orbitals above the N=82 shell closure.

The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay in $^{76}$Ge with two modular arrays of natural and $^{76}$Ge-enriched germanium detectors. It is located at the 4850 level of Sanford Underground Research Facility in Lead, South Dakota, USA, and its total mass of germanium detectors is 44.1 kg, of which 29.7 kg is enriched. The analysis of the first 26 kg-yr of data provides an unprecedented energy resolution of 0.13% in the region of interest at 2039 keV and a background level of 15.4 $\pm$ 2.0 counts/(FWHM t yr). It establishes the lower limit of the half-life of neutrinoless double beta decay as 2.7 10$^{25}$ yr in 76Ge at 90% CL. This analysis will be summarized here with an emphasis on the energy determination., MEDEX'19 proceedings. Since it was send to AIP, the last reference was published: S. I. Alvis et al. (Majorana Collaboration) Phys. Rev. C 100, 025501

Author(s): Cuesta, C; Alvis, SI; Arnquist, IJ; Avignone, FT; Barabash, AS; Barton, CJ; Basu, V; Bertrand, FE; Bos, B; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Clark, M; Cuesta, C; Detwiler, JA; Efremenko, Y; Ejiri, H; Elliott, SR; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Haufe, CR; Hegedus, RJ; Hehn, L; Henning, R; Hervas Aguilar, D; Hoppe, EW; Howe, MA; Kidd, MF; Konovalov, SI; Kouzes, RT; Lopez, AM; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; Othman, G; Pettus, W; Piliounis, A; Poon, AWP; Radford, DC; Rager, J; Reine, AL; Rielage, K; Ruof, NW; Shanks, B; Shirchenko, M; Tedeschi, D; Varner, RL; Vasilyev, S; White, BR; Wilkerson, JF; Wiseman, C; Xu, W; Yakushev, E; Yu, CH; Yumatov, V; Zhitnikov, I; Zhu, BX | Abstract: The Majorana Collaboration is operating an array of high-purity Ge detectors to search for the neutrinoless double-β decay of Ge76. The Majorana Demonstrator consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in Ge76) split between two modules constructed from ultraclean materials. Both modules are contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota. We present updated results on the search for neutrinoless double-β decay in Ge76 with 26.0±0.5 kg yr of enriched exposure. With the Demonstrator's energy resolution of 2.53 keV FWHM at Qββ, which is the best among all neutrinoless double-β decay experiments, we observe one event in the region of interest with 0.65 events expected from the estimated background, resulting in a lower limit on the Ge76 neutrinoless double-β decay half-life of 2.7×1025 yr [90% confidence level (CL)] with a median sensitivity of 4.8×1025 yr (90% CL). Depending on the matrix elements used, a 90% CL upper limit on the effective Majorana neutrino mass in the range of 200-433 meV is obtained. The measured background in the configurations with full shielding and optimized grounding is 11.9±2.0 counts/(FWHM t yr).

This Letter reports the first measurement of the ^{235}U ν[over ¯]_{e} energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MW_{th} highly enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) ν[over ¯]_{e}-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to ^{235}U. Despite broad agreement, comparison of the Huber ^{235}U model to the measured spectrum produces a χ^{2}/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured ^{235}U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the ν[over ¯]_{e} energy region of 5-7 MeV.

The Precision Reactor Oscillation and Spectrum (PROSPECT) Experiment is a reactor neutrino experiment designed to search for sterile neutrinos with a mass on the order of 1 eV/c$^2$ and to measure the spectrum of electron antineutrinos from a highly-enriched $^{235}$U nuclear reactor. The PROSPECT detector consists of an 11 by 14 array of optical segments in $^{6}$Li-loaded liquid scintillator at the High Flux Isotope Reactor in Oak Ridge National Laboratory. Antineutrino events are identified via inverse beta decay and read out by photomultiplier tubes located at the ends of each segment. The detector response is characterized using a radioactive source calibration system. This paper describes the design, operation, and performance of the PROSPECT source calibration system.

The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay in 76Ge using arrays of point-contact germanium detectors operating at the Sanford Underground Research Facility. Background results in the neutrinoless double-beta decay region of interest from data taken during construction, commissioning, and the start of full operations have been recently published. A pulse shape analysis cut applied to achieve this result, named AvsE, is described in this paper. This cut is developed to remove events whose waveforms are typical of multi-site energy deposits while retaining (90 +/- 3.5)% of single-site events. This pulse shape discrimination is based on the relationship between the maximum current and energy, and tuned using 228Th calibration source data. The efficiency uncertainty accounts for variation across detectors, energy, and time, as well as for the position distribution difference between calibration and $0\nu\beta\beta$ events, established using simulations., Comment: 8 pages, 8 figures

The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between $E_x = 4$ and 5 MeV in $^{19}$Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2$^-$ and 7/2$^-$, respectively. Gamma-ray transitions from these states were studied using triton-$\gamma$-$\gamma$ coincidences from the $^{19}$F($^{3}$He,$t\gamma$)$^{19}$Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the $J^\pi$ values are actually 7/2$^-$ and 9/2$^-$, respectively. These assignments are consistent with the values in the $^{19}$F mirror nucleus and in contrast to previously accepted assignments.

This Letter reports the first measurement of the ^{235}U ν[over ¯]_{e} energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MW_{th} highly enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) ν[over ¯]_{e}-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to ^{235}U. Despite broad agreement, comparison of the Huber ^{235}U model to the measured spectrum produces a χ^{2}/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured ^{235}U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the ν[over ¯]_{e} energy region of 5-7 MeV.

A direct test of nova explosion models comes from the observation of γ rays created in the decay of radioactive isotopes produced in the nova. One such isotope, 18F, is believed to be the main source of observable γ rays at and below 511 keV. The main destruction mechanism of 18F is thought to be the 18F(p,α)15O reaction, and uncertainties in the reaction rate arise from uncertainties in the energies, spins, and parities of the nuclear levels in 19Ne above the 18F+p threshold. To measure the properties of these levels, the 19F(3He,t)19Ne∗(γ) reaction was studied at Argonne National Laboratory and the Nuclear Science Laboratory at the University of Notre Dame.A direct test of nova explosion models comes from the observation of γ rays created in the decay of radioactive isotopes produced in the nova. One such isotope, 18F, is believed to be the main source of observable γ rays at and below 511 keV. The main destruction mechanism of 18F is thought to be the 18F(p,α)15O reaction, and uncertainties in the reaction rate arise from uncertainties in the energies, spins, and parities of the nuclear levels in 19Ne above the 18F+p threshold. To measure the properties of these levels, the 19F(3He,t)19Ne∗(γ) reaction was studied at Argonne National Laboratory and the Nuclear Science Laboratory at the University of Notre Dame.

The MAJORANA Collaboration is constructing the MAJORANA Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in Ge-76. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of the MAJORANA Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of the high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the MAJORANA Demonstrator was characterized and the micro-discharge effects during the MAJORANA Demonstrator commissioning phase were studied. A stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge., 9 pages, 12 figures, 8 tables, submitted to NIM A

Author(s): Guinn, IS; Arnquist, IJ; Avignone, FT; Barabash, AS; Barton, CJ; Bertrand, FE; Bos, B; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Clark, ML; Cuesta, C; Detwiler, JA; Drobizhev, A; Edwins, DW; Efremenko, Y; Ejiri, H; Elliott, SR; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guiseppe, VE; Haufe, CR; Hegedus, RJ; Henning, R; Hervas Aguilar, D; Hoppe, EW; Hostiuc, A; Kidd, MF; Kim, I; Kouzes, RT; Lopez, AM; Lopez-Castano, JM; Martin, EL; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; Oli, TK; Othman, G; Pettus, W; Poon, AWP; Radford, DC; Rager, J; Reine, AL; Rielage, K; Ruof, NW; Stortini, MJ; Tedeschi, D; Varner, RL; Wilkerson, JF; Wiseman, C; Xu, W; Yu, CH; Zhu, BX | Abstract: The MAJORANA DEMONSTRATOR is searching for double-beta decay of 76Ge to excited states (E.S.) in 76Se using a modular array of high purity Germanium detectors. 76Ge can decay into three E.S.s of 76Se. The E.S. decays have a clear event signature consisting of a ββ-decay with the prompt emission of one or two γ-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of (0.56 2.1) ⋅ 1024 y. In particular, for the 2v transition to the first 0+ E.S. of 76Se, a lower half-life limit of 0.68 ⋅ 1024 at 90% CL was achieved.

Author(s): Haufe, CR; Reine, AL; Abgrall, N; Alvis, SI; Arnquist, IJ; Avignone, FT; Barabash, AS; Barton, CJ; Bertrand, FE; Bode, T; Bradley, AW; Brudanin, V; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Cuesta, C; Detwiler, JA; Dunagan, C; Efremenko, Y; Ejiri, H; Elliott, SR; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Hehn, L; Henning, R; Hoppe, EW; Howe, MA; Keeter, KJ; Kidd, MF; Konovalov, SI; Kouzes, RT; Lopez, AM; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; O'Shaughnessy, C; Othman, G; Pettus, W; Poon, AWP; Radford, DC; Rager, J; Rielage, K; Robertson, RGH; Ruof, NW; Shanks, B; Shirchenko, M; Suriano, AM; Tedeschi, D; Trimble, JE; Varner, RL; Vasilyev, S; Vetter, K; Vorren, K; White, BR; Wilkerson, JF; Wiseman, C; Xu, W; Yakushev, E; Yu, CH; Yumatov, V; Zhitnikov, I; Zhu, BX | Abstract: The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decays in germanium-76 and to demonstrate the feasibility to deploy a ton-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and 76Ge-enriched germanium p-Type point contact detectors totaling 44.1 kg, located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. The DEMONSTRATOR uses custom high voltage cables to bias the detectors, as well as custom signal cables and connectors to read out the charge deposited at each detectors point contact. These low-mass cables and connectors must meet stringent radiopurity requirements while being subjected to thermal and mechanical stress. A number of issues have been identified with the currently installed cables and connectors. An improved set of cables and connectors for the MAJORANA DEMONSTRATOR are being developed with the aim of increasing their overall reliability and connectivity. We will discuss some of the issues encountered with the current cables and connectors as well as our improved designs and their initial performance.

Author(s): Gilliss, T; Abgrall, N; Alvis, SI; Arnquist, IJ; Avignone, FT; Barabash, AS; Barton, CJ; Bertrand, FE; Bode, T; Bradley, AW; Brudanin, V; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Cuesta, C; Detwiler, JA; Dunagan, C; Efremenko, Y; Ejiri, H; Elliott, SR; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Haufe, CR; Hehn, L; Henning, R; Hoppe, EW; Howe, MA; Keeter, KJ; Kidd, MF; Konovalov, SI; Kouzes, RT; Lopez, AM; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; O'Shaughnessy, C; Othman, G; Pettus, W; Poon, AWP; Radford, DC; Rager, J; Reine, AL; Rielage, K; Robertson, RGH; Ruof, NW; Shanks, B; Shirchenko, M; Suriano, AM; Tedeschi, D; Trimble, JE; Varner, RL; Vasilyev, S; Vetter, K; Vorren, K; White, BR; Wilkerson, JF; Wiseman, C; Xu, W; Yakushev, E; Yu, CH; Yumatov, V; Zhitnikov, I; Zhu, BX | Abstract: The MAJORANA DEMONSTRATOR is a 76Ge-based neutrinoless double-beta decay (0νββ) experiment. Staged at the 4850 ft level of the Sanford Underground Research Facility, the DEMONSTRATOR operates an array of high-purity p-Type point contact Ge detectors deployed within a graded passive shield and an active muon veto system. The present work concerns the two-neutrino double-beta decay mode (2νββ) of 76Ge. For Ge detectors, having superior energy resolution (0.1%), this mode poses negligible background to the 0νββ mode, even for a ton-scale experiment. However, the measurement of the 2νββ mode allows for careful systematics checks of active detector mass, enrichment fraction, and pulse shape discrimination cuts related to both the 0νββ and 2νββ decay modes. A precision measurement of the 2νββ shape also allows searches for spectral distortions, possibly indicative of new physics, including 0νββχ. Work is underway to construct a full experimental background model enabling a Bayesian fit to the measured energy spectrum and extraction of a precise 2νββ spectrum and half-life.

Author(s): Elliott, SR; Abgrall, N; Arnquist, IJ; Avignone, FT; Barabash, AS; Bertrand, FE; Bradley, AW; Brudanin, V; Busch, M; Buuck, M; Caldwell, TS; Chan, YD; Christofferson, CD; Chu, PH; Cuesta, C; Detwiler, JA; Dunagan, C; Efremenko, Y; Ejiri, H; Fullmer, A; Galindo-Uribarri, A; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Henning, R; Hoppe, EW; Howe, MA; Jasinski, BR; Keeter, KJ; Kidd, MF; Konovalov, SI; Kouzes, RT; Leon, J; Lopez, AM; Macmullin, J; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Orrell, JL; O'Shaughnessy, C; Poon, AWP; Radford, DC; Rager, J; Rielage, K; Robertson, RGH; Romero-Romero, E; Shanks, B; Shirchenko, M; Suriano, AM; Tedeschi, D; Trimble, JE; Varner, RL; Vasilyev, S; Vetter, K; Vorren, K; White, BR; Wilkerson, JF; Wiseman, C; Xu, W; Yakushev, E; Yu, CH; Yumatov, V; Zhitnikov, I | Abstract: Neutrinoless double-beta decay searches seek to determine the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator is composed of 44.8 kg (29.7 kg enriched in 76Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals of the Demonstrator are to establish the required background and scalability of a Ge-based, next-generation, tonne-scale experiment. Following a commissioning run that began in 2015, the first detector module started physics data production in early 2016. We will discuss initial results of the Module 1 commissioning and first physics run, as well as the status and potential physics reach of the full Majorana Demonstrator experiment. The collaboration plans to complete the assembly of the second detector module by mid-2016 to begin full data production with the entire array.

Detection of nuclear-decay γ rays provides a sensitive thermometer of nova nucleosynthesis. The most intense γ-ray flux is thought to be annihilation radiation from the β^{+} decay of ^{18}F, which is destroyed prior to decay by the ^{18}F(p,α)^{15}O reaction. Estimates of ^{18}F production had been uncertain, however, because key near-threshold levels in the compound nucleus, ^{19}Ne, had yet to be identified. We report the first measurement of the ^{19}F(^{3}He,tγ)^{19}Ne reaction, in which the placement of two long-sought 3/2^{+} levels is suggested via triton-γ-γ coincidences. The precise determination of their resonance energies reduces the upper limit of the rate by a factor of 1.5-17 at nova temperatures and reduces the average uncertainty on the nova detection probability by a factor of 2.1.

The Majorana Demonstrator is an ultralow-background experiment searching for neutrinoless double-beta decay in [superscript 76]Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. Free, relativistic, lightly ionizing particles with an electrical charge less than e are forbidden by the standard model but predicted by some of its extensions. If such particles exist, they might be detected in the Majorana Demonstrator by searching for multiple-detector events with individual-detector energy depositions down to 1 keV. This search is background-free, and no candidate events have been found in 285 days of data taking. New direct-detection limits are set for the flux of lightly ionizing particles for charges as low as e/1000., National Science Foundation (U.S.) (Grant MRI-0923142), National Science Foundation (U.S.) (Grant PHY-1003399), National Science Foundation (U.S.) (Grant PHY-1102292), National Science Foundation (U.S.) (Grant PHY1206314), National Science Foundation (U.S.) (Grant PHY-1614611), Los Alamos National Laboratory. Laboratory Directed Research and Development Program, Pacific Northwest National Laboratory (U.S.). Laboratory Directed Research and Development Program, Russian Foundation for Basic Research (Grant 15-02- 02919), Natural Sciences and Engineering Research Council of Canada (SAPIN-2017-00023), Canada Foundation for Innovation

The Majorana Demonstrator is an ultralow-background experiment searching for neutrinoless double-beta decay in ^{76}Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. Free, relativistic, lightly ionizing particles with an electrical charge less than e are forbidden by the standard model but predicted by some of its extensions. If such particles exist, they might be detected in the Majorana Demonstrator by searching for multiple-detector events with individual-detector energy depositions down to 1 keV. This search is background-free, and no candidate events have been found in 285 days of data taking. New direct-detection limits are set for the flux of lightly ionizing particles for charges as low as e/1000.

The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decay in $^{76}$Ge and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modules of natural and $^{76}$Ge-enriched germanium detectors totalling 44.1 kg, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Commissioning of the experiment began in June 2015, followed by data production with the full detector array in August 2016. The ultra-low background and record energy resolution achieved by the MAJORANA DEMONSTRATOR enable a sensitive neutrinoless double-beta decay search, as well as additional searches for physics beyond the Standard Model. I will discuss the design elements that enable these searches, along with the latest results, focusing on the neutrinoless double-beta decay search. I will also discuss the current status and the future plans of the MAJORANA DEMONSTRATOR, as well as the plans for a future tonne-scale $^{76}$Ge experiment., 4 pages. Proceedings of The 39th International Conference on High Energy Physics (ICHEP2018), 4-11 July, 2018, Seoul, Korea. Submitted to Proceedings of Science

The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in ^{76}Ge. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in ^{76}Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Q_{ββ} and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×10^{25} yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0_{-2.5}^{+3.1} counts/(FWHM t yr).

The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-β decay in ^{76}Ge. The Majorana Demonstrator comprises 44.1 kg of Ge detectors (29.7 kg enriched in ^{76}Ge) split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. We achieve unprecedented energy resolution of 2.5 keV FWHM at Q_{ββ} and a very low background with no observed candidate events in 9.95 kg yr of enriched Ge exposure, resulting in a lower limit on the half-life of 1.9×10^{25} yr (90% C.L.). This result constrains the effective Majorana neutrino mass to below 240-520 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4.0_{-2.5}^{+3.1} counts/(FWHM t yr).

The Majorana Demonstrator is an array of point-contact Ge detectors fabricated from Ge isotopically enriched to 88% in 76 Ge to search for neutrinoless double beta decay. The processing of Ge for germanium detectors is a well-known technology. However, because of the high cost of Ge enriched in 76 Ge special procedures were required to maximize the yield of detector mass and to minimize exposure to cosmic rays. These procedures include careful accounting for the material; shielding it to reduce cosmogenic generation of radioactive isotopes; and development of special reprocessing techniques for contaminated solid germanium, shavings, grindings, acid etchant and cutting fluids from detector fabrication. Processing procedures were developed that resulted in a total yield in detector mass of 70%. However, none of the acid-etch solution and only 50% of the cutting fluids from detector fabrication were reprocessed. Had they been processed, the projections for the recovery yield would be between 80% and 85%. Maximizing yield is critical to justify a possible future ton-scale experiment. A process for recovery of germanium from the acid-etch solution was developed with yield of about 90%. All material was shielded or stored underground whenever possible to minimize the formation of 68 Ge by cosmic rays, which contributes background in the double-beta decay region of interest and cannot be removed by zone refinement and crystal growth. Formation of 68 Ge was reduced by a significant factor over that in natural abundance detectors not protected from cosmic rays.

This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of $^{235}$U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4 ton $^6$Li-doped liquid scintillator detector covering a baseline range of 7-9 m from the reactor and operating under less than 1 meter water equivalent overburden. Data collected during 33 live-days of reactor operation at a nominal power of 85 MW yields a detection of 25461 $\pm$ 283 (stat.) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5$\sigma$ statistical significance within two hours of on-surface reactor-on data-taking. A reactor-model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the Reactor Antineutrino Anomaly at 2.2$\sigma$ confidence level., Comment: 7 pages, 5 figures; v3: Added additional supplemental files

The Majorana Collaboration is using an array of high-purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. Searches for neutrinoless double-beta decay are understood to be the only viable experimental method for testing the Majorana nature of the neutrino. Observation of this decay would imply violation of lepton number, that neutrinos are Majorana in nature, and provide information on the neutrino mass. The Majorana Demonstrator comprises 44.1 kg of p-type point-contact Ge detectors (29.7 kg enriched in 76Ge) surrounded by a low-background shield system. The experiment achieved a high efficiency of converting raw Ge material to detectors and an unprecedented detector energy resolution of 2.5 keV FWHM at Q$_{\beta\beta}$. The Majorana collaboration began taking physics data in 2016. This paper summarizes key construction aspects of the Demonstrator and shows preliminary results from initial data., Comment: 5 pages, 2 figures. Proceeding for the "16th International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16)", 18-22 September 2017

The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make both a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and to probe eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long baselines. PROSPECT utilizes a segmented $^6$Li-doped liquid scintillator detector for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT is a movable 4-ton antineutrino detector covering distances of 7m to 13m from the High Flux Isotope Reactor core. It will probe the best-fit point of the $\bar\nu_e$ disappearance experiments at 4$\sigma$ in 1 year and the favored regions of the sterile neutrino parameter space at more than 3$\sigma$ in 3 years. PROSPECT will test the origin of spectral deviations observed in recent $\theta_{13}$ experiments, search for sterile neutrinos, and address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly. This paper describes the design, construction, and commissioning of PROSPECT and reports first data characterizing the performance of the PROSPECT antineutrino detector., Comment: 30 pages, 33 figures; updated with journal revision and reference

A new type of gaseous micropattern particle detector based on a closed-cell microcavity plasma panel sensor is reported. The first device was fabricated with 1 x 1 x 2 mm cells. It has shown very clean signals of 0.6 to 2.5 volt amplitude, fast rise time of approximately 2 ns and FWHM of about 2 ns with very uniform signal shapes across all pixels. From initial measurements with beta particles from a radioactive source, a maximum pixel efficiency of greater than 95% is calculated, for operation of the detector over a 100V wide span of high voltages (HV). Over this same HV range, the background rate per pixel was measured to be 3 to 4 orders of magnitude lower than the rate with the cell illuminated by the beta source. Pixel-to-pixel count rate uniformity is within 3% and stable within 3% for many days. The time resolution is 2.4 ns, and a very low cell-to-cell crosstalk has been measured between cells separated by 2 mm., Comment: Submitted to NIM

The Majorana Collaboration is constructing a system containing 40kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements.

The MAJORANA DEMONSTRATOR will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope 76Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the 76Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolution performances. We present here the low-noise low- background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the MAJORANA DEMONSTRATOR. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.

High purity germanium (HPGe) crystals will be used for the MAJORANA DEMONSTRATOR, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performance of the HPGe crystals. A variety of crystal properties are being investigated, including basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distributions. In this paper, we will present our measurements that characterize the HPGe crystals. We will also discuss our simulation package for the detector characterization setup, and show that additional information can be extracted from data-simulation comparisons., Comment: To appear in the Proceedings of the 13th International Conference on Topics in Astroparticle and Underground Physics, TAUP 2013 (F. Avignone & W. Haxton, editors, Physics Procedia, Elsevier)