Papers by Vladislav Kobychev
arXiv (Cornell University), Dec 9, 2014
Proceedings of XV International Workshop on Neutrino Telescopes — PoS(Neutel 2013), 2014
Proceedings of XV International Workshop on Neutrino Telescopes — PoS(Neutel 2013), 2014
The unmatched radio-purity of its liquid scintillator and the large detector size make Borexino a... more The unmatched radio-purity of its liquid scintillator and the large detector size make Borexino an ideal apparatus for the study of neutrino oscillations at very short distance and, particularly, for the search of sterile neutrinos of mass scale of the order of 1 eV. We present here three possible experiments with neutrino and anti-neutrino artificial sources located close to or inside the Borexino detector and discuss their sensitivity to sterile neutrinos. Expected sensitivities on electron neutrino magnetic moment, electroweak mixing angle, and couplings to axial and vector currents are shown as well.
Proceedings of XVII International Workshop on Neutrino Telescopes — PoS(NEUTEL2017), 2018
Solar neutrinos have played a central role in the discovery of the neutrino oscillation mechanism... more Solar neutrinos have played a central role in the discovery of the neutrino oscillation mechanism. They still are proving to be a unique tool to help investigate the fusion reactions that power stars and further probe basic neutrino properties. The Borexino neutrino observatory has been operationally acquiring data at Laboratori Nazionali del Gran Sasso in Italy since 2007. Its main goal is the real-time study of low energy neutrinos (solar or originated elsewhere, such as geo-neutrinos). The latest analysis of experimental data, taken during the so-called Borexino Phase-II (2011-present), will be showcased in this talk - yielding new high-precision, simultaneous wide band flux measurements of the four main solar neutrino components belonging to the "pp" fusion chain (pp, pep, 7Be, 8B), as well as upper limits on the remaining two solar neutrino fluxes (CNO and hep).
EPJ Web of Conferences, 2016
Acta Physica Polonica A, 2010
Recently ZnWO4 was proposed as perspective material for low-counting experiments to search for ra... more Recently ZnWO4 was proposed as perspective material for low-counting experiments to search for rare processes. Such experiments demand high radiopurity of ZnWO4 crystal scintillators. With this aim radioactive contamination of large volume (0.1-0.7 kg) ZnWO4 crystal scintillators were measured in the underground Laboratori Nazionali del Gran Sasso of the INFN at the depth of ≈ 3600 m water equivalent.
Solar neutrino with Borexino: Results and perspectives
Physics of Particles and Nuclei, 2015
Search for 5.5 MeV solar axions produced in a, p(d, 3He)A reaction with Borexino detector
New limits on heavy sterile neutrino mixing in B8 decay obtained with the Borexino detector
Phys. Rev. D, 2014
Borexino has been running since May 2007 at the LNGS laboratory in Italy with the primary goal of... more Borexino has been running since May 2007 at the LNGS laboratory in Italy with the primary goal of detecting solar neutrinos. The detector, a large, unsegmented liquid scintillator calorimeter characterized by unprecedented low levels of intrinsic radioactivity, is optimized for the study of the lower energy part of the spectrum. During the Phase-I (2007-2010), Borexino first detected and then precisely measured the flux of the 7 Be solar neutrinos, ruled out any significant day-night asymmetry of their interaction rate, made the first direct observation of the pep neutrinos, and set the tightest upper limit on the flux of CNO solar neutrinos. In this paper we discuss the signal signature and provide a comprehensive description of the backgrounds, quantify their event rates, describe the methods for their identification, selection or subtraction, and describe data analysis. Key features are an extensive in situ calibration program using radioactive sources, the detailed modeling of the detector response, the ability to define an innermost fiducial volume with extremely low background via software cuts, and the excellent pulse-shape discrimination capability of the scintillator that allows particle identification. We report a measurement of the annual modulation of the 7 Be neutrino interaction rate. The period, the amplitude, and the phase of the observed modulation are consistent with the solar origin of these events, and the absence of their annual modulation is rejected with higher than 99% C.L. The physics implications of Phase-I results in the context of the neutrino oscillation physics and solar models are presented.
Development of CdWO4 crystal scintillators from enriched isotopes for 2γ-decay experiments
Cadmium tungstate crystal scintillators enriched in <sup>106</sup>Cd (<sup>106&... more Cadmium tungstate crystal scintillators enriched in <sup>106</sup>Cd (<sup>106</sup>CdWO<inf>4</inf>) and <sup>116</sup>Cd (<sup>116</sup>CdWO<inf>4</inf>) have been developed to search for 2β-decay of <sup>106</sup>Cd and <sup>116</sup>Cd.
Development of radiopure cadmium tungstate crystal scintillators from enriched 106Cd and 116Cd to search for double beta decay
ABSTRACT Cadmium tungstate crystal scintillators enriched in 106Cd up to 66% ( 106CdWO4 ) and in ... more ABSTRACT Cadmium tungstate crystal scintillators enriched in 106Cd up to 66% ( 106CdWO4 ) and in 116Cd up to 82% ( 116CdWO4 ) have been developed. The low radioactive contamination of the crystals measured on the level of ≤ 1.5 mBq/kg ( 40K ), ≤ 0.005 - 0.012 mBq/kg ( 226Ra ), 0.04 - 0.07 mBq/kg ( 228Th ) allows to carry out high sensitivity experiments to search for double beta processes in 106Cd and 116Cd .
Search for 2β decay of 116Cd with the help of enriched 116CdWO4 crystal scintillators
EPJ Web of Conferences, 2014
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2010
Geo-neutrinos, electron anti-neutrinos produced in β decays of naturally occurring radioactive is... more Geo-neutrinos, electron anti-neutrinos produced in β decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. We report the first observation at more than 3σ C.L. of geo-neutrinos, performed with the Borexino detector at Laboratori Nazionali del Gran Sasso. Anti-neutrinos are detected through the neutron inverse β decay reaction. With a 252.6 ton•yr fiducial exposure after all selection cuts, we detected 9.9 +4.1 −3.4 (+14.6 −8.2) geo-neutrino events, with errors corresponding to a 68.3% (99.73%) C.L. From the ln L profile, the statistical significance of the Borexino geo-neutrino observation corresponds to a 99.997% C.L. Our measurement of the geo-neutrinos rate is 3.9 +1.6 −1.3 (+5.8 −3.2) events/(100 ton•yr). The observed prompt positron spectrum above 2.6 MeV is compatible with that expected from european nuclear reactors (mean base line of approximately 1000 km). Our measurement of reactor anti-neutrinos excludes the non-oscillation hypothesis at 99.60% C.L. This measurement rejects the hypothesis of an active geo-reactor in the Earth's core with a power above 3 TW at 95% C.L.
Journal of Instrumentation, 2011
Borexino, a liquid scintillator detector at LNGS, is designed for the detection of neutrinos and ... more Borexino, a liquid scintillator detector at LNGS, is designed for the detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear reactors, and the Earth. The feeble nature of these signals requires a strong suppression of backgrounds below a few MeV. Very low intrinsic radiogenic contamination of all detector components needs to be accompanied by the efficient identification of muons and of muon-induced backgrounds. Muons produce unstable nuclei by spallation processes along their trajectory through the detector whose decays can mimic the expected signals; for isotopes with half-lives longer than a few seconds, the dead time induced by a muon-related veto becomes unacceptably long, unless its application can be restricted to a sub-volume along the muon track. Consequently, not only the identification of muons with very high efficiency but also a precise reconstruction of their tracks is of primary importance for the physics program of the experiment. The Borexino inner detector is surrounded by an outer water-Čerenkov detector that plays a fundamental role in accomplishing this task. The detector design principles and their implementation are described. The strategies adopted to identify muons are reviewed and their efficiency is evaluated. The overall muon veto efficiency is found to be 99.992 % or better. Adhoc track reconstruction algorithms developed are presented. Their performance is tested against muon events of known direction such as those from the CNGS neutrino beam, test tracks available from a dedicated External Muon Tracker and cosmic muons whose angular distribution reflects the local overburden profile. The achieved angular resolution is ∼3 •-5 • and the lateral resolution is ∼35-50 cm, depending on the impact parameter of the crossing muon. The methods implemented to efficiently tag cosmogenic neutrons are also presented.
Journal of Instrumentation, 2011
Double β experiments with the help of scintillation and HPGe detectors at Gran Sasso
AIP Conference Proceedings, 2011
Journal of High Energy Physics, 2013
The very low radioactive background of the Borexino detector, its large size, and the well proved... more The very low radioactive background of the Borexino detector, its large size, and the well proved capability to detect both low energy electron neutrinos and antineutrinos make an ideal case for the study of short distance neutrino oscillations with artificial sources at Gran Sasso. This paper describes the possible layouts of 51Cr (ν e ) and 144Ce-144Pr $$ \left( {{{\overline{\nu}}_e}} \right) $$ source experiments in Borexino and shows the expected sensitivity to eV mass sterile neutrinos for three possible different phases of the experiment. Expected results on neutrino magnetic moment, electroweak mixing angle, and couplings to axial and vector currents are shown too.
Radiation Measurements, 2013
Cadmium tungstate crystal scintillators enriched in 106 Cd and 116 Cd were developed. The produce... more Cadmium tungstate crystal scintillators enriched in 106 Cd and 116 Cd were developed. The produced scintillators exhibit good optical and scintillation properties, and a low level of radioactive contamination. Experiments to search for double beta decay of 106 Cd and 116 Cd are in progress at the Gran Sasso National Laboratories of the INFN (Italy). Prospects to further improve the radiopurity of the detectors by recrystallization are discussed.