Ethan Brown
Associate Professor Rensselaer Polytechnic Institute
- Troy NY
Astrophysicist investigating the search for Dark Matter with XENON experiments and Neutrinoless Double Beta Decay with the nEXO experiment.
Rensselaer Polytechnic Institute
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Areas of Expertise
Biography
As a member of the XENON100, XENON1T, XENONnT, and DARWIN dark matter experiments, and also the nEXO neutrinoless double beta decay experiment, his research focuses on development of techniques for operating high purity xenon detectors, including purification and diagnostics, as well as novel radiopure electrodes based on thin films.
His research group also works on simulations and data analysis looking for new physics with these experiments.
Education
University of California Los Angeles
Ph.D.
Physics
University of California San Diego
B.Sc.
Physics
Media Appearances
RPI professor earns grant from DOE
News10 ABC tv
2022-09-21
Rensselaer Polytechnic Institute’s (RPI) Ethan Brown, an associate professor of physics, applied physics, and astronomy, has received a $280,000 grant from the Department of energy. The grant will aid the nEXO experiment in the research of Neutrinoless Double Beta Decay (NDBD) which Brown is a part.
Filling the Void: What Is Dark Matter?
Popular Mechanics print
2022-03-23
The most mysterious stuff in the universe could hold the very key to understanding it.
Dark Matter Hunters Observe 'Rarest Event Ever Recorded'
Newsweek print
2019-04-24
Researchers have measured a process that takes more than one trillion times the age of the universe to complete, using an instrument built to search for dark matter—the most elusive particle known to man.
... "We have shown that we can observe the rarest events ever recorded," Brown told Newsweek. "The key finding is that an isotope formerly thought to be completely stable has now been shown to decay on an unimaginably long timescale."
Articles
Dark Matter Search Results from a One Tonne×Year Exposure of XENON1T
arXivE. Aprile et al (XENON Collaboration)
2018-09-13
We report on a search for Weakly Interacting Massive Particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber with a fiducial mass of (1.30±0.01) t, resulting in a 1.0 t×yr exposure. The energy region of interest, [1.4, 10.6] keVee ([4.9, 40.9] keVnr), exhibits an ultra-low electron recoil background rate of (82+5−3 (sys)±3 (stat)) events/(t×yr×keVee). No significant excess over background is found and a profile likelihood analysis parameterized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross-section for WIMP masses above 6 GeV/c2, with a minimum of 4.1×10−47 cm2 at 30 GeV/c2 and 90% confidence level.
Excess electronic recoil events in XENON1T
Physical Review DE. Aprile et al (XENON Collaboration)
2020-10-01
We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 tonne-years and an unprecedentedly low background rate of 76±2stat events/(tonne×year×keV) between 1 and 30 keV, the data enable one of the most sensitive searches for solar axions, an enhanced neutrino magnetic moment using solar neutrinos, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4σ significance, and a three-dimensional 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by gae
Projected WIMP sensitivity of the XENONnT dark matter experiment
Journal of Cosmology and Astroparticle PhysicsE. Aprile et al (XENON Collaboration)
2020-11-02
XENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict the experimental background and project the sensitivity of XENONnT to the detection of weakly interacting massive particles (WIMPs). The expected average differential background rate in the energy region of interest, corresponding to (1, 13) keV and (4, 50) keV for electronic and nuclear recoils, amounts to 12.3 ± 0.6 (keV t y)-1 and (2.2± 0.5)× 10−3 (keV t y)-1, respectively, in a 4 t fiducial mass. We compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. With the exposure goal of 20 t y, the expected sensitivity to spin-independent WIMP-nucleon interactions reaches a cross-section of 1.4×10−48 cm2 for a 50 GeV/c2 mass WIMP at 90% confidence level, more than one order of magnitude beyond the current best limit, set by XENON1T . In addition, we show that for a 50 GeV/c2 WIMP with cross-sections above 2.6×10−48 cm2 (5.0×10−48 cm2) the median XENONnT discovery significance exceeds 3σ (5σ). The expected sensitivity to the spin-dependent WIMP coupling to neutrons (protons) reaches 2.2×10−43 cm2 (6.0×10−42 cm2).
222Rn emanation measurements for the XENON1T experiment
The European Physical Journal CE. Aprile et al (XENON Collaboration)
2021-04-20
The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the 222Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a 222Rn activity concentration of 10μBq/kg in 3.2t of xenon. The knowledge of the distribution of the 222Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the 222Rn activity concentration in XENON1T. The final 222Rn activity concentration of (4.5±0.1)μBq/kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.
nEXO: neutrinoless double beta decay search beyond 10 to the 28th year half-life sensitivity
Journal of Physics G: Nuclear and Particle PhysicsG Adhikari et al
2021-12-03
The nEXO neutrinoless double beta (0νββ) decay experiment is designed to use a time projection chamber and 5000 kg of isotopically enriched liquid xenon to search for the decay in 136Xe. Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of 1028 years. Specifically, improvements have been made in the understanding of production of scintillation photons and charge as well as of their transport and reconstruction in the detector. The more detailed knowledge of the detector construction has been paired with more assays for trace radioactivity in different materials. In particular, the use of custom electroformed copper is now incorporated in the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Furthermore, a number of assumptions from previous sensitivity projections have gained further support from interim work validating the nEXO experiment concept. Together these improvements and updates suggest that the nEXO experiment will reach a half-life sensitivity of 1.35 × 1028 yr at 90% confidence level in 10 years of data taking, covering the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. The effects of backgrounds deviating from the nominal values used for the projections are also illustrated, concluding that the nEXO design is robust against a number of imperfections of the model.
