Á. Chavarría
A5050708124- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Particle Detector Development and Performance
- Particle physics theoretical and experimental studies
- Astrophysics and Cosmic Phenomena
- CCD and CMOS Imaging Sensors
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- Cosmology and Gravitation Theories
- Seismic Waves and Analysis
- Radioactive Decay and Measurement Techniques
- Astronomy and Astrophysical Research
- Radioactivity and Radon Measurements
- Radiation Therapy and Dosimetry
- Seismic Imaging and Inversion Techniques
- Atmospheric Ozone and Climate
- Advanced Fiber Optic Sensors
- Radioactive contamination and transfer
- Nuclear physics research studies
- Quantum, superfluid, helium dynamics
- Scientific Research and Discoveries
- Electron and X-Ray Spectroscopy Techniques
- Machine Fault Diagnosis Techniques
University of Washington
2019-2024
Campbell Collaboration
2022
University of Chicago
2013-2020
Fermi National Accelerator Laboratory
2014-2020
Princeton University
2008-2016
Istituto Nazionale di Fisica Nucleare
2014
Kurchatov Institute
2013
Joint Institute for Nuclear Research
2013
Petersburg Nuclear Physics Institute
2013
A direct measurement of the 0.862 MeV 7Be solar neutrino interaction rate performed with Borexino detector at Laboratori Nazionali del Gran Sasso yields 46.0$\pm1.5_{\rm stat}$$^{+1.6}_{-1.5\,\rm syst}$ counts/day/(100 tons). Our result is first a sub-MeV an accuracy better than 5%. The hypothesis no oscillation for neutrinos rejected 4.9$\sigma$ C.L. Using latest Standard Solar Model (SSM) flux predictions, leads directly to precise determination survival probability $\nu_e$'s in vacuum,...
We report the direct measurement of 7Be solar neutrino signal rate performed with Borexino detector at Laboratori Nazionali del Gran Sasso. The interaction 0.862 MeV neutrinos is 49+/-3stat+/-4syst counts/(day.100 ton). hypothesis no oscillation for inconsistent our 4sigma C.L. Our result first survival probability nu(e) in transition region between matter-enhanced and vacuum-driven oscillations. improves experimental determination flux 7Be, pp, CNO nu(e), limit on effective magnetic moment...
We report the measurement of electron neutrino elastic scattering from 8B solar neutrinos with 3 MeV energy threshold by Borexino detector in Gran Sasso (Italy). The rate neutrino-induced events above this is 0.217 +- 0.038 (stat) 0.008 (syst) cpd/100 t, which corresponds to equivalent unoscillated flux (2.4 0.4 0.1 (syst))x10^6 cm^-2 s^-1, good agreement measurements SNO and SuperKamiokaNDE. Assuming predicted high metallicity Standard Solar Model, average survival probability measured be...
Borexino has been running since May 2007 at the LNGS with primary goal of detecting solar neutrinos. The detector, a large, unsegmented liquid scintillator calorimeter characterized by unprecedented low levels intrinsic radioactivity, is optimized for study lower energy part spectrum. During Phase-I (2007-2010) first detected and then precisely measured flux 7Be neutrinos, ruled out any significant day-night asymmetry their interaction rate, made direct observation pep set tightest upper...
We observed, for the first time, solar neutrinos in 1.0-1.5 MeV energy range. measured rate of pep neutrino interactions Borexino to be [3.1+-0.6(stat)+-0.3(syst)] counts/(day x 100 ton) and provided a constraint on CNO interaction <7.9 (95% C.L.). The absence signal is disfavored at 99.97% C.L., while 98% C.L. This unprecedented sensitivity was achieved by adopting novel data analysis techniques rejection cosmogenic 11C, dominant background 1-2 region. Assuming MSW-LMA solution...
We report the first results of DarkSide-50, a direct search for dark matter operating in underground Laboratori Nazionali del Gran Sasso (LNGS) and searching rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The detector is Liquid Argon Time Projection Chamber with (46.4+-0.7) kg active mass, operated inside 30 t organic liquid scintillator neutron veto, which turn installed at center 1 kt water Cherenkov veto residual flux cosmic rays. here null...
We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based a method that exploits the extremely low levels of leakage current DAMIC detector at SNOLAB 2-6$\times$10$^{-22}$ A cm$^{-2}$. evaluate charge distribution pixels collect $<10~\rm{e^-}$ for contributions beyond may be attributed to interactions. Constraints placed so-far unexplored parameter space masses between 0.6 and 100 MeV$c^{-2}$. also present new hidden-photon in...
Many low-threshold experiments observe sharply rising event rates of yet unknown origins below a few hundred eV, and larger than expected from known backgrounds. Due to the significant impact this excess on dark matter or neutrino sensitivity these experiments, collective effort has been started share knowledge about individual observations. For this, EXCESS Workshop was initiated. In its first iteration in June 2021, ten rare search collaborations contributed initiative via talks...
We report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed an integrated exposure 85.23 g days, and exploits subelectron charge resolution low level current charge-coupled devices (CCDs). Dark-matter-induced ionization signals above detector are searched for in CCD pixels up to 7e^{-}. With this dataset we place limits mass between 0.53 1000 MeV/c^{2}, excluding unexplored regions...
Geo-neutrinos, electron anti-neutrinos produced in beta decays of naturally occurring radioactive isotopes the Earth, are a unique direct probe our planet's interior. We report first observation at more than 3$\sigma$ C.L. geo-neutrinos, performed with Borexino detector Laboratori Nazionali del Gran Sasso. Anti-neutrinos detected through neutron inverse decay reaction. With 252.6 ton-yr fiducial exposure after all selection cuts, we 9.9^{+4.1}_{-3.4}(^{+14.6}_{-8.2}) geo-neutrino events,...
We present results of a dark matter search performed with 0.6 kg d exposure the DAMIC experiment at SNOLAB underground laboratory. measure energy spectrum ionization events in bulk silicon charge-coupled devices down to signal 60 eV electron equivalent. The data are consistent radiogenic backgrounds, and constraints on spin-independent WIMP-nucleon elastic-scattering cross section accordingly placed. A region parameter space relevant potential from CDMS-II Si is excluded using same target...
A bstract The very low radioactive background of the Borexino detector, its large size, and well proved capability to detect both energy electron neutrinos antineutrinos make an ideal case for study short distance neutrino oscillations with artificial sources at Gran Sasso. This paper describes possible layouts 51 Cr ( ν e ) 144 Ce- Pr $$ \left( {{{\overline{\nu}}_e}} \right) source experiments in shows expected sensitivity eV mass sterile three different phases experiment. Expected results...
We present a measurement of the geo--neutrino signal obtained from 1353 days data with Borexino detector at Laboratori Nazionali del Gran Sasso in Italy. With fiducial exposure (3.69 $\pm$ 0.16) $\times$ $10^{31}$ proton year after all selection cuts and background subtraction, we detected (14.3 4.4) geo-neutrino events assuming fixed chondritic mass Th/U ratio 3.9. This corresponds to $S_{geo}$ = (38.8 12.0) TNU just 6 $10^{-6}$ probability for null measurement. U Th left as free parameters...
We present direct detection constraints on the absorption of hidden-photon dark matter with particle masses in range $1.2--30\text{ }\mathrm{eV}\text{ }{c}^{\ensuremath{-}2}$ DAMIC experiment at SNOLAB. Under assumption that local is entirely constituted hidden photons, sensitivity to kinetic mixing parameter $\ensuremath{\kappa}$ competitive from solar emission, reaching a minimum value $2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$ $17\text{ }\text{ }{c}^{\ensuremath{-}2}$....
We present constraints on the existence of weakly interacting massive particles (WIMPs) from an 11 kg-day target exposure DAMIC experiment at SNOLAB underground laboratory. The observed energy spectrum and spatial distribution ionization events with electron-equivalent energies $>$200 eV$_{\rm ee}$ in CCDs are consistent backgrounds natural radioactivity. An excess is above analysis threshold 50 ee}$. While origin this low-energy requires further investigation, our data exclude...
Dark matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth’s bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal detectors sensitive DM-electron interactions. Here, we report results obtained from first underground operation of DAMIC-M prototype detector searching for such MeV-scale mass. A model-independent analysis finds no rate <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...
Borexino, a liquid scintillator detector at LNGS, is designed for the detection of neutrinos and antineutrinos from Sun, supernovae, nuclear reactors, Earth. The feeble nature these signals requires strong suppression backgrounds below few MeV. Very low intrinsic radiogenic contamination all components needs to be accompanied by efficient identification muons muon-induced backgrounds. Muons produce unstable nuclei spallation processes along their trajectory through whose decays can mimic...
We have measured the muon flux at underground Gran Sasso National Laboratory (3800 m w.e.) to be (3.41 \pm 0.01) \times 10-4m-2s-1 using four years of Borexino data. A modulation this signal is observed with a period (366\pm3) days and relative amplitude (1.29 0.07)%. The phase (179 6) days, corresponding maximum on 28th June. Using most complete atmospheric data models available, rate fluctuations are shown positively correlated temperature, an effective coefficient {\alpha}T = 0.93 0.04....
A search for 5.5-MeV solar axions produced in the $p+d\rightarrow\rm{^3He}+A (5.5 \rm{MeV})$ reaction was performed using Borexino detector. The Compton conversion of to photons, ${\rm A}+e\rightarrow e+\gamma$; axio-electric effect, A}+e+Z\rightarrow e+Z$; decay into two A}\rightarrow2\gamma$; and inverse Primakoff on nuclei, A}+Z\rightarrow\gamma+Z$, are considered. Model independent limits axion-electron ($g_{Ae}$), axion-photon ($g_{A\gamma}$), isovector axion-nucleon ($g_{3AN}$)...
We report a measurement of the ionization efficiency silicon nuclei recoiling with sub-keV kinetic energy in bulk charge-coupled device (CCD). Nuclear recoils are produced by low-energy neutrons ($<24\text{ }\text{ }\mathrm{keV}$) from $^{124}\mathrm{Sb}\text{\ensuremath{-}}^{9}\mathrm{Be}$ photoneutron source, and their signal is measured down to 60 eV electron equivalent. This range, previously unexplored, relevant for detection low-mass dark matter particles. The found deviate...