A. Etenko - Academia.edu (original) (raw)

Papers by A. Etenko

Physical Review D, 2010

We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy th... more We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.217 ± 0.038(stat) ± 0.008(syst) cpd/100 t, which corresponds to Φ ES 8 B = 2.4 ± 0.4± 0.1×10 6 cm −2 s −1 , in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the 8 B neutrino flux predicted by the high metallicity Standard Solar Model, the average 8 B νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for 7 Be and 8 B neutrinos as measured by Borexino differ by 1.9 σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar νe survival probability Pee between the low energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

Physics Letters B, 1998

Initial results are presented from CHOOZ 1 , a long-baseline reactor-neutrino vacuum-oscillation ... more Initial results are presented from CHOOZ 1 , a long-baseline reactor-neutrino vacuum-oscillation experiment. The data reported here were taken during the period March to October 1997, when the two reactors ran at combined power levels varying from zero to values approaching their full rated power of 8.5 GW (thermal). Electron antineutrinos from the reactors were detected by a liquid scintillation calorimeter located at a distance of about 1 km. The detector was constructed in a tunnel protected from cosmic rays by a 300 MWE rock overburden. This massive shielding strongly reduced potentially troublesome backgrounds due to cosmic-ray muons, leading to a background rate of about one event per day, more than an order of magnitude smaller than the observed neutrino signal. From the statistical agreement between detected and expected neutrino event rates, we find (at 90% confidence level) no evidence for neutrino oscillations in the ν e disappearance mode for the parameter region given approximately by ∆m 2 > 0.9 10 −3 eV 2 for maximum mixing and sin 2 2θ > 0.18 for large ∆m 2 .

Physical Review D, 2010

We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy th... more We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.217 ± 0.038(stat) ± 0.008(syst) cpd/100 t, which corresponds to Φ ES 8 B = 2.4 ± 0.4± 0.1×10 6 cm −2 s −1 , in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the 8 B neutrino flux predicted by the high metallicity Standard Solar Model, the average 8 B νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for 7 Be and 8 B neutrinos as measured by Borexino differ by 1.9 σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar νe survival probability Pee between the low energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

Physical Review D, 1999

The CHOOZ experiment 1 has measured the antineutrino flux at about 1 Km from two nuclear reactors... more The CHOOZ experiment 1 has measured the antineutrino flux at about 1 Km from two nuclear reactors to search for possible ν e → ν x oscillations with mass-squared differences as low as 10 −3 eV 2 for full mixing. We show that the analysis of the ∼ 2700 ν e -events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture ≈ 18 • at the 68% C.L. . We discuss the implications of this result for locating a supernova explosion.

Nuclear Physics B - Proceedings Supplements, 2009

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

Borexino, a large volume detector for low energy neutrino spectroscopy, is currently running unde... more Borexino, a large volume detector for low energy neutrino spectroscopy, is currently running underground at the Laboratori Nazionali del Gran Sasso, Italy. The main goal of the experiment is the real-time measurement of sub MeV solar neutrinos, and particularly of the mono energetic (862 keV) 7 Be electron capture neutrinos, via neutrinoelectron scattering in an ultra-pure liquid scintillator. This paper is mostly devoted to the description of the detector structure, the photomultipliers, the electronics, and the trigger and calibration systems. The real performance of the detector, which always meets, and sometimes exceeds, design expectations, is also shown. Some important aspects of the Borexino project, i.e. the fluid handling plants, the purification techniques and the filling procedures, are not covered in this paper and are, or will be, published elsewhere (see Introduction and Bibliography).

Journal of Physics: Conference Series, 2012

Solar Standard Models predict spectra, fluxes of solar ν Solar Neutrino experiments can test SSM ... more Solar Standard Models predict spectra, fluxes of solar ν Solar Neutrino experiments can test SSM 4 Solar Standard Model predicted ν fluxes Small uncertainties Large uncertainties Tension between High and Low Metallicity SSM High Z SSM (GS) → older model, higher heavy element abundances, agrees with helioseismology Low Z SSM (AGS) → new model based on solar atmospheric spectroscopy, lower heavy element abundances, does not agree with helioseismology 5 Solar Neutrino Propagation Solar neutrinos (ν e ) undergo oscillation Interaction with matter can affect oscillation (Wolfenstein) The oscillation probability can be enhanced by a resonance (Mikheyev & Smirnov) Energy Dependent Survival Probability P ee If SSM predicts ν flux with high precision → probe neutrino oscillations 6 MSW Oscillation Regimes In these regimes, P ee depends only on θ 12 , not on the mass splitting or the details of the neutrino-matter interaction Bahcall & Peña-Garay Matter enhanced Phaseaveraged vacuum oscillations Solar Neutrino Propagation MSW-LMA scenario: current understanding of solar neutrino oscillation Physics beyond Standard Model can affect Energy dependence of P ee 8 B 7 Be pp Matter Enhanced Region Vacuum Dominated Region 8 Solar Neutrino and Astrophysics wish list  Particle physics: -Test MSW-LMA P ee with high accuracy -Probe the P ee in the transition region, sensitive to Physics beyond Standard Model  Solar Astrophysics: -Test SSM predictions, prove CNO cycle in Sun -Test two competing models of SSM: High and Low Metallicity 9 10 pep ν measurement motivations pep neutrino flux predicted with high precision: 1.2% SSM uncertainty pep neutrino energy (1.44 MeV) in P ee transition region, sensitive to Physics beyond the Standard Model Allows for more stringent tests of oscillation models 11 CNO ν measurement motivations Detecting CNO ν prove that CNO cycle happens in Sun Abundance of heavy elements in Sun have high impact on CNO ν flux magnitude Test of High vs Low Z SSM CNO FLUX (10 8 cm -2 s -1 ) HIGH Z SSM 5.24 ± 0.84 LOW Z SSM 3.76 ± 0.60

Astroparticle Physics, 2013

As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototy... more As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get consistent light yields averaging 8.887±0.003(stat)±0.444(sys) p.e./keV ee . With additional purification, the light yield measured at 511 keV increased to 9.142±0.006(stat) p.e./keV ee .

Astroparticle Physics, 2002

The techniques researched, developed and applied towards the measurement of radioisotope concentr... more The techniques researched, developed and applied towards the measurement of radioisotope concentrations at ultralow levels in the real-time solar neutrino experiment BOREXINO at Gran Sasso are presented and illustrated with specific results of widespread interest. We report the use of low-level germanium gamma spectrometry, low-level miniaturized gas proportional counters and low background scintillation detectors developed in solar neutrino research. Each now sets records in its field. We additionally describe our techniques of radiochemical ultra-pure, few atom manipulations and extractions. Forefront measurements also result from the powerful combination of neutron activation and low-level counting. Finally, with our techniques and commercially available mass spectrometry and atomic absorption spectroscopy, new low-level detection limits for isotopes of interest are obtained. Ó

In the core of the Sun, energy is released through sequences of nuclear reactions that convert hy... more In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun's energy and contributing to the discovery of neutrino oscillations, those from proton-proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84 × 10(33) ergs per second, is generated by the proton-proton fusion process.

Physical Review D, 2010

We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy th... more We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.217 ± 0.038(stat) ± 0.008(syst) cpd/100 t, which corresponds to Φ ES 8 B = 2.4 ± 0.4± 0.1×10 6 cm −2 s −1 , in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the 8 B neutrino flux predicted by the high metallicity Standard Solar Model, the average 8 B νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for 7 Be and 8 B neutrinos as measured by Borexino differ by 1.9 σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar νe survival probability Pee between the low energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

Physics Letters B, 1998

Initial results are presented from CHOOZ 1 , a long-baseline reactor-neutrino vacuum-oscillation ... more Initial results are presented from CHOOZ 1 , a long-baseline reactor-neutrino vacuum-oscillation experiment. The data reported here were taken during the period March to October 1997, when the two reactors ran at combined power levels varying from zero to values approaching their full rated power of 8.5 GW (thermal). Electron antineutrinos from the reactors were detected by a liquid scintillation calorimeter located at a distance of about 1 km. The detector was constructed in a tunnel protected from cosmic rays by a 300 MWE rock overburden. This massive shielding strongly reduced potentially troublesome backgrounds due to cosmic-ray muons, leading to a background rate of about one event per day, more than an order of magnitude smaller than the observed neutrino signal. From the statistical agreement between detected and expected neutrino event rates, we find (at 90% confidence level) no evidence for neutrino oscillations in the ν e disappearance mode for the parameter region given approximately by ∆m 2 > 0.9 10 −3 eV 2 for maximum mixing and sin 2 2θ > 0.18 for large ∆m 2 .

Physical Review D, 2010

We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy th... more We report the measurement of ν-e elastic scattering from 8 B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.217 ± 0.038(stat) ± 0.008(syst) cpd/100 t, which corresponds to Φ ES 8 B = 2.4 ± 0.4± 0.1×10 6 cm −2 s −1 , in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the 8 B neutrino flux predicted by the high metallicity Standard Solar Model, the average 8 B νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for 7 Be and 8 B neutrinos as measured by Borexino differ by 1.9 σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar νe survival probability Pee between the low energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

Physical Review D, 1999

The CHOOZ experiment 1 has measured the antineutrino flux at about 1 Km from two nuclear reactors... more The CHOOZ experiment 1 has measured the antineutrino flux at about 1 Km from two nuclear reactors to search for possible ν e → ν x oscillations with mass-squared differences as low as 10 −3 eV 2 for full mixing. We show that the analysis of the ∼ 2700 ν e -events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture ≈ 18 • at the 68% C.L. . We discuss the implications of this result for locating a supernova explosion.

Nuclear Physics B - Proceedings Supplements, 2009

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

Borexino, a large volume detector for low energy neutrino spectroscopy, is currently running unde... more Borexino, a large volume detector for low energy neutrino spectroscopy, is currently running underground at the Laboratori Nazionali del Gran Sasso, Italy. The main goal of the experiment is the real-time measurement of sub MeV solar neutrinos, and particularly of the mono energetic (862 keV) 7 Be electron capture neutrinos, via neutrinoelectron scattering in an ultra-pure liquid scintillator. This paper is mostly devoted to the description of the detector structure, the photomultipliers, the electronics, and the trigger and calibration systems. The real performance of the detector, which always meets, and sometimes exceeds, design expectations, is also shown. Some important aspects of the Borexino project, i.e. the fluid handling plants, the purification techniques and the filling procedures, are not covered in this paper and are, or will be, published elsewhere (see Introduction and Bibliography).

Journal of Physics: Conference Series, 2012

Solar Standard Models predict spectra, fluxes of solar ν Solar Neutrino experiments can test SSM ... more Solar Standard Models predict spectra, fluxes of solar ν Solar Neutrino experiments can test SSM 4 Solar Standard Model predicted ν fluxes Small uncertainties Large uncertainties Tension between High and Low Metallicity SSM High Z SSM (GS) → older model, higher heavy element abundances, agrees with helioseismology Low Z SSM (AGS) → new model based on solar atmospheric spectroscopy, lower heavy element abundances, does not agree with helioseismology 5 Solar Neutrino Propagation Solar neutrinos (ν e ) undergo oscillation Interaction with matter can affect oscillation (Wolfenstein) The oscillation probability can be enhanced by a resonance (Mikheyev & Smirnov) Energy Dependent Survival Probability P ee If SSM predicts ν flux with high precision → probe neutrino oscillations 6 MSW Oscillation Regimes In these regimes, P ee depends only on θ 12 , not on the mass splitting or the details of the neutrino-matter interaction Bahcall & Peña-Garay Matter enhanced Phaseaveraged vacuum oscillations Solar Neutrino Propagation MSW-LMA scenario: current understanding of solar neutrino oscillation Physics beyond Standard Model can affect Energy dependence of P ee 8 B 7 Be pp Matter Enhanced Region Vacuum Dominated Region 8 Solar Neutrino and Astrophysics wish list  Particle physics: -Test MSW-LMA P ee with high accuracy -Probe the P ee in the transition region, sensitive to Physics beyond Standard Model  Solar Astrophysics: -Test SSM predictions, prove CNO cycle in Sun -Test two competing models of SSM: High and Low Metallicity 9 10 pep ν measurement motivations pep neutrino flux predicted with high precision: 1.2% SSM uncertainty pep neutrino energy (1.44 MeV) in P ee transition region, sensitive to Physics beyond the Standard Model Allows for more stringent tests of oscillation models 11 CNO ν measurement motivations Detecting CNO ν prove that CNO cycle happens in Sun Abundance of heavy elements in Sun have high impact on CNO ν flux magnitude Test of High vs Low Z SSM CNO FLUX (10 8 cm -2 s -1 ) HIGH Z SSM 5.24 ± 0.84 LOW Z SSM 3.76 ± 0.60

Astroparticle Physics, 2013

As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototy... more As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get consistent light yields averaging 8.887±0.003(stat)±0.444(sys) p.e./keV ee . With additional purification, the light yield measured at 511 keV increased to 9.142±0.006(stat) p.e./keV ee .

Astroparticle Physics, 2002

The techniques researched, developed and applied towards the measurement of radioisotope concentr... more The techniques researched, developed and applied towards the measurement of radioisotope concentrations at ultralow levels in the real-time solar neutrino experiment BOREXINO at Gran Sasso are presented and illustrated with specific results of widespread interest. We report the use of low-level germanium gamma spectrometry, low-level miniaturized gas proportional counters and low background scintillation detectors developed in solar neutrino research. Each now sets records in its field. We additionally describe our techniques of radiochemical ultra-pure, few atom manipulations and extractions. Forefront measurements also result from the powerful combination of neutron activation and low-level counting. Finally, with our techniques and commercially available mass spectrometry and atomic absorption spectroscopy, new low-level detection limits for isotopes of interest are obtained. Ó

In the core of the Sun, energy is released through sequences of nuclear reactions that convert hy... more In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun's energy and contributing to the discovery of neutrino oscillations, those from proton-proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84 × 10(33) ergs per second, is generated by the proton-proton fusion process.