Sophia J. Hollick
A5032032945- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Nuclear Physics and Applications
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Ionosphere and magnetosphere dynamics
- Stellar, planetary, and galactic studies
- Geomagnetism and Paleomagnetism Studies
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Solid-state spectroscopy and crystallography
- Nuclear reactor physics and engineering
- Advanced NMR Techniques and Applications
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Atomic and Molecular Physics
- Nuclear physics research studies
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Terahertz technology and applications
- Luminescence Properties of Advanced Materials
Yale University
2020-2024
Brookhaven National Laboratory
2023
University of New Hampshire
2017-2022
Rensselaer Polytechnic Institute
2020
COSINE-100 is a direct detection dark matter experiment that aims to test DAMA/LIBRA's claim of discovery by searching for dark-matter-induced annual modulation signal with NaI(Tl) detectors. We present new constraints on the from dataset 2.82 yr livetime utilizing an active mass 61.3 kg total exposure 173 kg⋅yr. This result features improved event selection allows both lowering energy threshold 1 keV and more precise time-dependent background model. In 1–6 2–6 intervals, we observe best-fit...
We report on the search for weakly interacting massive particle (WIMP) dark matter candidates in galactic halo that interact with sodium and iodine nuclei COSINE-100 experiment produce energetic electrons accompany recoil via Migdal effect. The WIMP mass sensitivity of previous searches relied detection ionization signals produced by target recoiling from elastic WIMP-nucleus scattering was restricted to masses above $\sim$5 GeV/$c^2$ detectors' 1 keVee energy-electron-equivalent threshold....
Abstract The DAMA/LIBRA collaboration has reported the observation of an annual modulation in event rate that been attributed to dark matter interactions over last two decades. However, even though tremendous efforts detect similar were pursued, no definitive evidence observed corroborate signal. Many studies assuming various models have attempted reconcile DAMA/LIBRA’s signals and null results from other experiments, however clear conclusion can be drawn. Apart hypothesis, several examined...
Abstract We present a comprehensive study of the nonproportionality NaI(Tl) scintillation detectors within context dark matter search experiments. Our investigation, which integrates COSINE-100 data with supplementary $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> spectroscopy, measures light yields across diverse energy levels from full-energy peaks produced by decays various isotopes. These interest were supported both long and...
Abstract We adopt the theory for turbulent transport of energy by solar wind fluctuations and apply that to observations Voyager 1 2 spacecraft obtain rates thermal proton heating are controlled two sources: large-scale in arise from sources excitation waves newborn interstellar ions. In process, we compute magnetic spectra 839 data intervals spanning range 35 au when ion is available use those independent estimates cascade at intermediate scales assume equals rate turbulence. compare three...
Abstract We examine both Voyager and Advanced Composition Explorer magnetic field measurements at frequencies that characterize the inertial range evaluate anisotropy of fluctuations as they relate to compressive component underlying wavevector turbulence. The fluctuation it relates is directly dependent upon plasma beta thermal proton ratio magnitude strength mean field. This has been seen before 1 au. in plane perpendicular field, which a measure distribution, should depend on angle...
The performance of nuclear reactors and other systems depends on a precise understanding the neutron interaction cross sections for materials used in these systems. These exhibit resonant structure whose shape is determined part by angular-momentum quantum numbers resonances. correct assignment resonances is, therefore, paramount. In this project, we apply machine learning to automate number assignments using only resonances' energies widths not relying detailed transmission or capture...
Abstract In this companion paper, we describe low-frequency magnetic waves observed in 637 intervals of Voyager 1 and 2 data from launch late 1977 through 1990. By the end 1990 spacecraft reached 43.5 au, while reaches 33.6 au. The are attributed to newborn interstellar pickup He + H . analysis follow idea put forward by Cannon et al. followed Fisher Aggarwal wherein necessary condition for observation is that wave growth rate exceeds background turbulence rate. We explore build on...
Abstract We have surveyed the Voyager magnetic field data from launch through 1990 in search of low-frequency waves that are excited by newborn interstellar pickup ions (PUIs). During this time 1 and 2 spacecraft reached 43.5 33.6 au, respectively. The use daily spectrograms permits us to perform a thorough data. identified 637 different intervals show evidence either He + , H or both, these extend furthest distances years studied. To compare wave features against more typical interplanetary...
Abstract As part of a published effort to study low-frequency magnetic waves excited by newborn interstellar pickup ions seen the Voyager spacecraft, we developed set control intervals that represent background turbulence when observations are not dominated wave excitation. This paper begins an better understand solar wind from 1 45 au while spanning greater than one cycle. We first focus on diagnostics marking onset dissipation. includes expected break in power spectrum at frequencies...
Abstract We examine both Voyager and Advanced Composition Explorer magnetic field measurements at frequencies that characterize the inertial range using traditional polarization techniques are designed to plasma waves. Although we find good agreement with anticipated spectral index of power spectrum scaling heliocentric distance, do not analyses yield results can be readily described by wave theory. The fluctuations circularly polarized there is a markedly reduced coherence between...
We present results from a search for solar bosonic dark matter using the annual modulation method with COSINE-100 experiment. The were interpreted considering three sector bosons models: photons, Dine-Fischler-Srednicki-Zhitnisky (DFSZ) and Kim-Shifman-Vainshtein-Zakharov (KSVZ) axions, Kaluza-Klein axions. No signal compatible expected models was found dataset of 2.82 yr, 61.3 kg NaI(Tl) crystals. Therefore, we set 90% confidence level upper limits each studied. For photon model, most...
In our companion papers we analyze 637 intervals of magnetic wave activity observed by the Voyager 1 and 2 spacecraft from its launch in 1977 through end 1990. We argue that these waves originate cyclotron resonance with newborn interstellar pickup He+ H+. As list events is long potentially useful to other researchers, take this opportunity times those here, along their heliocentric location, ellipticity (often referred as polarization), whether thermal ion data available PLS instrument. A...
Abstract We report two observations of magnetic waves due to He + pickup ions observed by the Voyager 2 spacecraft in mid-1989 demonstrate that such occur as far out ∼30 au from Sun. The are sufficiently planets, interplanetary shocks, and other possible sources energetic particles make newborn interstellar only likely explanation for source waves. Additionally, low-frequency might be expected a variety cometary species not seen. events studied here were picked preliminary list ∼300...
Wave excitation by newborn interstellar pickup ions (PUIs) plays a significant role in theories that attempt to describe IBEX and Voyager observations the solar wind heliosheath. The same dynamic processes can be far-reaching extend into inner heliosphere at least 1AU likely smaller heliocentric distances. While high-resolution magnetic field measurements required study these waves are not yet available heliosheath, we have studied range of found evidence due PUIs using ACE (1998–2015 1 AU),...
Abstract COSINE-100 is a direct dark matter search experiment, with the primary goal of testing annual modulation signal observed by DAMA/LIBRA, using same target material, NaI(Tl). In previous analyses, we achieved 1 keV energy threshold used in DAMA/LIBRA's analysis that reported an 11.6 σ significance. this article, report improved lowered to 0.7 keV, thanks application Multi-Layer Perception network and new likelihood parameter waveforms frequency domain. The lower would enable better...
The production of radioactive isotopes by interactions cosmic-ray particles with sodium iodide (NaI) crystals can produce backgrounds in detectors used to search for rare events. Through controlled irradiation NaI a neutron beam that matches the spectrum, followed direct counting and fitting resulting spectrum across broad range energies, we determined integrated rate several long-lived radioisotopes. measurements were then extrapolated determine sea-level cosmogenic activation rate,...
We have surveyed the Voyager 1 and 2 spacecraft magnetic field data from launch in 1977 through 1990 using daily spectrograms to find suitably long intervals eliminate times near transients or strong gradients that might not represent homogeneous turbulence intervals. In process, we also omitted when waves due suprathermal particle populations such as interstellar pickup ions can be seen. Our goal was construct a database of interplanetary spectra could used our companion papers study...
We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using COSINE-100 array of NaI(Tl) crystal detectors at Yangyang Underground Laboratory. The signal would be an excess events with energies above 4 MeV over well-understood background. Because no are observed in a 97.7 kg·yr exposure, we set limits on BDM interactions under variety hypotheses. Notably, explored photon parameter space, leading to competitive compared direct...
Abstract We report here observations of magnetic waves recorded by the Voyager spacecraft in solar wind near Jupiter that are possibly result excitation newborn pickup H + . Consideration growth rates due to known interstellar ion sources strongly disfavor an source. To determine likely source waves, we compute minimum production rate equating wave turbulent cascade and derive a lower limit for at times observations. The only available neutral these levels required is Jovian system, most...