J. I. Collar
A5003687777- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Neutrino Physics Research
- Atomic and Subatomic Physics Research
- Cosmology and Gravitation Theories
- Radiation Detection and Scintillator Technologies
- Astrophysics and Cosmic Phenomena
- Nuclear Physics and Applications
- Scientific Research and Discoveries
- Astronomy and Astrophysical Research
- CCD and CMOS Imaging Sensors
- Physics of Superconductivity and Magnetism
- Radiation Therapy and Dosimetry
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Superconducting and THz Device Technology
- Superconducting Materials and Applications
- Nuclear physics research studies
- Photocathodes and Microchannel Plates
- Advanced Semiconductor Detectors and Materials
- Nuclear reactor physics and engineering
- Distributed and Parallel Computing Systems
- Age of Information Optimization
- Computational Physics and Python Applications
University of Chicago
2014-2023
Fermi National Accelerator Laboratory
2014-2023
Donostia International Physics Center
2023
Indiana University South Bend
2010
University of Illinois Chicago
2008-2009
Centre National de la Recherche Scientifique
1996-2003
Université Paris Cité
1996-2003
Sorbonne Université
1996-2003
European Organization for Nuclear Research
1996-2002
University of Lisbon
1996-2001
Hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in universe. Such particles are expected to emerge abundantly from hot interior of stars. To test this prediction, CERN Axion Solar Telescope (CAST) uses 9 T refurbished Large Hadron Collider magnet directed towards Sun. In strong magnetic field, solar axions can be converted X-ray photons which recorded by detectors. 2013–2015 run, thanks low-background detectors and new telescope,...
We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, number of cosmogenic peaks can be observed for first time. discuss irreducible excess bulklike events below 3 keV ionization energy. These could caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible determine their origin. Improved constraints are...
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest all low-energy neutrino couplings. This mode interaction offers new opportunities to study properties and leads a miniaturization detector size, with potential technological applications. We observed this process at 6.7σ confidence level, using low-background, 14.6-kilogram CsI[Na] scintillator exposed emissions from Spallation Neutron...
Fifteen months of cumulative CoGeNT data are examined for indications an annual modulation, a predicted signature weakly interacting massive particle (WIMP) interactions. Presently available support the presence modulated component unknown origin, with parameters prima facie compatible galactic halo composed light-mass WIMPs. Unoptimized estimators yield statistical significance modulation ∼2.8σ, limited by short exposure.
CoGeNT employs p-type point-contact (PPC) germanium detectors to search for Weakly Interacting Massive Particles (WIMPs). By virtue of its low energy threshold and ability reject surface backgrounds, this type device allows an emphasis on low-mass dark matter candidates (wimp mass about 10 GeV/c2). We report the characteristics PPC detector presently taking data at Soudan Underground Laboratory, elaborating aspects shielding, acquisition, instrumental stability, analysis, background...
We have searched for solar axions or similar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup with improved conditions in all detectors. From absence of excess X-rays when magnet was pointing Sun, we set an upper limit on axion-photon coupling 8.8 x 10^{-11} GeV^{-1} at 95% CL m_a <~ 0.02 eV. This result is best experimental over a broad range axion masses and eV also supersedes previous derived from energy-loss arguments globular-cluster stars.
New data are reported from the operation of a 4.0 kg CF$_{3}$I bubble chamber in 6800-foot-deep SNOLAB underground laboratory. The effectiveness ultrasound analysis discriminating alpha-decay background events single nuclear recoils has been confirmed, with lower bound $>$99.3% rejection events. Twenty recoil event candidates and three multiple were observed during total exposure 553 kg-days distributed over different nucleation thresholds. effective for recoil-like was 437.4 kg-days. A...
New results are reported from the operation of PICO-60 dark matter detector, a bubble chamber filled with 52 kg C_{3}F_{8} located in SNOLAB underground laboratory. As previous PICO chambers, exhibits excellent electron recoil and alpha decay rejection, observed multiple-scattering neutron rate indicates single-scatter background less than one event per month. A blind analysis an efficiency-corrected 1167-kg day exposure at 3.3-keV thermodynamic threshold reveals no single-scattering nuclear...
New data are reported from the operation of a 2 liter ${\mathrm{C}}_{3}{\mathrm{F}}_{8}$ bubble chamber in SNOLAB underground laboratory, with total exposure 211.5 kg days at four different energy thresholds below 10 keV. These show that provides excellent electron-recoil and alpha rejection capabilities very low thresholds. The exhibits an sensitivity $<3.5\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}10}$ factor $>98.2%$. also include first observation dependence acoustic signal on...
Final results are reported from operation of the PICO-60 C$_3$F$_8$ dark matter detector, a bubble chamber filled with 52 kg located in SNOLAB underground laboratory. The was operated at thermodynamic thresholds as low 1.2 keV without loss stability. A new blind 1404-kg-day exposure 2.45 threshold acquired approximately same expected total background rate previous 1167-kg-day 3.3 keV. This increased is enabled part by optical tracking analysis to better identify events near detector walls,...
Hypothetical axionlike particles with a two-photon interaction would be produced in the sun by Primakoff process. In laboratory magnetic field ("axion helioscope"), they transformed into x-rays energies of few keV. Using decommissioned Large Hadron Collider test magnet, CERN Axion Solar Telescope ran for about 6 months during 2003. The first results from analysis these data are presented here. No signal above background was observed, implying an upper limit to axion-photon coupling...
A new type of radiation detector, a p-type modified electrode germanium diode, is presented. It shown that the prototype displays, for first time, combination features (mass, energy threshold and background expectation) required measurement coherent neutrino–nucleus scattering in nuclear reactor experiment. First results are presented from its calibration using sub-kiloelectronvolt recoils similar to those expected antineutrinos or light WIMPs (weakly interacting massive particles) beyond...
We have searched for solar axions or other pseudoscalar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup. Whereas we previously reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here report where were filled 4He gas II) of variable pressure. The introduction generates a refractive photon mγ, thereby achieving maximum possible conversion rate those axion masses ma match mγ. With 160 different...
The Proceedings of the 2011 workshop on Fundamental Physics at Intensity Frontier. Science opportunities intensity frontier are identified and described in areas heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, nucleons, nuclei, atoms.
The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using 3He as a buffer gas. At T=1.8 K this allows larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with 4He. With about 1 h of data taking at each 252 different we have scanned the mass range 0.39 eV < m_a 0.64 eV. From absence excess X-rays when magnet was pointing Sun set typical upper limit on axion-photon coupling g_ag 2.3 x 10^{-10} GeV^{-1} 95% CL, exact...
Bubble Chambers provided the dominant particle detection technology in accelerator experiments for several decades, eventually falling into disuse with advent of other techniques. We report here on first period operation an ultra-clean, room-temperature bubble chamber containing 1.5 kg superheated CF$_{3}$I, a target maximally sensitive to spin-dependent and -independent Weakly Interacting Massive Particle (WIMP) couplings. An exposure excess 250 kg-days is obtained, live-time fraction...
A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type germanium detector to conclusively rule out standard isothermal galactic halo weakly interacting massive particles as explanation annual modulation effect leading claim. Bounds are similarly imposed on suggestion that pseudoscalars might lead effect. describe sensitivity light achievable with our device, particular, next-to-minimal supersymmetric model candidates.
In this paper, we study the recent excess of low-energy events observed by CoGeNT Collaboration and annual modulation reported DAMA/LIBRA Collaboration, discuss whether these signals could both be result same elastically scattering dark matter particle. We find that, without channeling but when taking into account uncertainties in relevant quenching factors, a candidate with mass approximately $7\text{ }\text{ }\mathrm{GeV}$ cross section nucleons...
The PICO collaboration reports results obtained by PICO-2L Run-2 after carefully controlling for particulate contamination. data clearly indicates that previously observed anomalies were due to contamination in the bubble chamber fluid. These observations set new bounds on spin-dependent scattering of dark matter, and help pave way larger scale experiments.
Data from the operation of a bubble chamber filled with 3.5 kg CF3I in shallow underground site are reported. An analysis ultrasound signals accompanying nucleations confirms that alpha decays generate significantly louder acoustic emission than single nuclear recoils, leading to an efficient background discrimination. Three dark matter candidate events were observed during effective exposure 28.1 day, consistent neutron background. This observation provides strong direct detection...
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the range 0.64 eV ≲ ma 1.17 eV. This closes gap to cosmological hot dark matter limit and actually overlaps it. From absence of excess x rays when magnet was pointing Sun we set a typical upper on axion-photon coupling gaγ 3.3 × 10(-10) GeV(-1) at 95% C.L., exact value depending pressure setting. Future direct axion searches will focus increasing sensitivity smaller values gaγ, example by...
New data are reported from the operation of PICO-60 dark matter detector, a bubble chamber filled with 36.8 kg CF$_3$I and located in SNOLAB underground laboratory. is largest to search for date. With an analyzed exposure 92.8 livedays, exhibits same excellent background rejection observed smaller chambers. Alpha decays exhibit frequency-dependent acoustic calorimetry, similar but not identical that recently C$_3$F$_8$ chamber. also observes large population unknown events, exhibiting...
The European Spallation Source (ESS), presently well on its way to completion, will soon provide the most intense neutron beams for multi-disciplinary science. Fortuitously, it also generate largest pulsed neutrino flux suitable detection of Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS), a process recently measured first time at ORNL's Neutron Source. We describe innovative detector technologies maximally able profit from order-of-magnitude increase in provided by ESS, along with...
The 96.4 day exposure of a 3 kg ultralow noise germanium detector to the high flux antineutrinos from power nuclear reactor is described. A very strong preference (p<1.2×10^{-3}) for presence coherent elastic neutrino-nucleus scattering (CEνNS) component in data found, when compared background-only model. No such effect visible 25 days operation during outages. best-fit CEνNS signal good agreement with expectations based on recent characterization response sub-keV recoils. Deviations order...