Научная группа: Borexino Collaboration
Загружается...
Участники
Funders
ID
Авторы
Персона
Скорохватов, Михаил Дмитриевич
Руководитель научной группы "Физика нейтрино и астрочастиц"
Публикации
Публикация
Открытый доступ
Modulations of the cosmic muon signal in ten years of Borexino data
(2019) Agostini, M.; Altenmueller, K.; Appel, S.; Atroshchenko, V.; Litvinovich, E.; Machulin, I.; Skorokhvatov, M.; Литвинович, Евгений Александрович; Мачулин, Игорь Николаевич; Скорохватов, Михаил Дмитриевич
We have measured the flux of cosmic muons in the Laboratori Nazionali del Gran Sasso at 3800 m.w.e. to be (3.432 +/- 0.003) center dot 10(-4) m(-2) s(-1) based on ten years of Borexino data acquired between May 2007 and May 2017. A seasonal modulation with a period of (366.3 +/- 0.6) d and a relative amplitude of (1.36 +/- 0.04)% is observed. The phase is measured to be (181.7 +/- 0.4) d, corresponding to a maximum at the 1 st of July. Using data inferred from global atmospheric models, we show the muon flux to be positively correlated with the atmospheric temperature and measure the e ff ective temperature coe ffi cient alpha(T) = 0.90 +/- 0.02. The origin of cosmic muons from pion and kaon decays in the atmosphere allows to interpret the e ff ective temperature coe ffi cient as an indirect measurement of the atmospheric kaon-topion production ratio r(K/pi) = 0.11(-0.07)(+0.11) for primary energies above 18TeV. We find evidence for a long-term modulation of the muon flux with a period of similar to 3000 d and a maximum in June 2012 that is not present in the atmospheric temperature data. A possible correlation between this modulation and the solar activity is investigated. The cosmogenic neutron production rate is found to show a seasonal modulation in phase with the cosmic muon flux but with an increased amplitude of (2.6 +/- 0.4)%.
Публикация
Только метаданные
Simultaneous precision spectroscopy of pp, Be 7, and pep solar neutrinos with Borexino Phase-II
(2019) Agostini, M.; Altenmuller, K.; Appel, S.; Atroshchenko, V.; Litvinovich, E.; Machulin, I.; Skorokhvatov, M.; Литвинович, Евгений Александрович; Мачулин, Игорь Николаевич; Скорохватов, Михаил Дмитриевич
© 2019 authors. Published by the American Physical Society.We present the simultaneous measurement of the interaction rates Rpp, RBe, Rpep of pp, Be7, and pep solar neutrinos performed with a global fit to the Borexino data in an extended energy range (0.19-2.93) MeV with particular attention to details of the analysis methods. This result was obtained by analyzing 1291.51 days of Borexino Phase-II data, collected after an extensive scintillator purification campaign. Using counts per day (cpd)/100 ton as unit, we find Rpp=134±10(stat)-10+6(sys), RBe=48.3±1.1(stat)-0.7+0.4(sys); and RpepHZ=2.43±0.36(stat)-0.22+0.15(sys) assuming the interaction rate RCNO of CNO-cycle (Carbon, Nitrogen, Oxigen) solar neutrinos according to the prediction of the high metallicity standard solar model, and RpepLZ=2.65±0.36(stat)-0.24+0.15(sys) according to that of the low metallicity model. An upper limit RCNO<8.1 cpd/100 ton (95% C.L.) is obtained by setting in the fit a constraint on the ratio Rpp/Rpep (47.7±0.8 cpd/100 ton or 47.5±0.8 cpd/100 ton according to the high or low metallicity hypothesis).
Публикация
Только метаданные
Comprehensive geoneutrino analysis with Borexino
(2020) Agostini, M.; Altenmuller, K.; Appel, S.; Atroshchenko, V.; Litvinovich, E.; Machulin, I.; Skorokhvatov, M.; Литвинович, Евгений Александрович; Мачулин, Игорь Николаевич; Скорохватов, Михаил Дмитриевич
© 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.This paper presents a comprehensive geoneutrino measurement using the Borexino detector, located at Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The analysis is the result of 3262.74 days of data between December 2007 and April 2019. The paper describes improved analysis techniques and optimized data selection, which includes enlarged fiducial volume and sophisticated cosmogenic veto. The reported exposure of (1.29±0.05)×1032 protons ×year represents an increase by a factor of two over a previous Borexino analysis reported in 2015. By observing 52.6-8.6+9.4(stat)-2.1+2.7(sys) geoneutrinos (68% interval) from U238 and Th232, a geoneutrino signal of 47.0-7.7+8.4(stat)-1.9+2.4(sys) TNU with -17.2+18.3% total precision was obtained. This result assumes the same Th/U mass ratio as found in chondritic CI meteorites but compatible results were found when contributions from U238 and Th232 were both fit as free parameters. Antineutrino background from reactors is fit unconstrained and found compatible with the expectations. The null-hypothesis of observing a geoneutrino signal from the mantle is excluded at a 99.0% C.L. when exploiting detailed knowledge of the local crust near the experimental site. Measured mantle signal of 21.2-9.0+9.5(stat)-0.9+1.1(sys) TNU corresponds to the production of a radiogenic heat of 24.6-10.4+11.1 TW (68% interval) from U238 and Th232 in the mantle. Assuming 18% contribution of K40 in the mantle and 8.1-1.4+1.9 TW of total radiogenic heat of the lithosphere, the Borexino estimate of the total radiogenic heat of the Earth is 38.2-12.7+13.6 TW, which corresponds to the convective Urey ratio of 0.78-0.28+0.41. These values are compatible with different geological predictions, however there is a ∼2.4σ tension with those Earth models which predict the lowest concentration of heat-producing elements in the mantle. In addition, by constraining the number of expected reactor antineutrino events, the existence of a hypothetical georeactor at the center of the Earth having power greater than 2.4 TW is excluded at 95% C.L. Particular attention is given to the description of all analysis details which should be of interest for the next generation of geoneutrino measurements using liquid scintillator detectors.
Публикация
Только метаданные
Improved measurement of B-8 solar neutrinos with 1.5 kt . y of Borexino exposure
(2020) Agostini, M.; Altenmuller, K.; Appel, S.; Atroshchenko, V.; Litvinovich, E.; Machulin, I.; Skorokhvatov, M.; Литвинович, Евгений Александрович; Мачулин, Игорь Николаевич; Скорохватов, Михаил Дмитриевич
We report on an improved measurement of the B-8 solar neutrino interaction rate with the Borexino experiment at the Laboratori Nazionali del Gran Sasso. Neutrinos are detected via their elastic scattering on electrons in a large volume of liquid scintillator. The measured rate of scattered electrons above 3 MeV of energy is 0.223(-0.016)(+0.015) (stat) (+0.006)(-0.006) (syst) cpd/100 t, which corresponds to an observed solar neutrino flux assuming no neutrino flavor conversion of Phi(ES)(8B) = 2.57(-0.18)(+0.17) (stat) (+0.07)(-0.07) (syst) x 10(6) cm(-2) s(-1). This measurement exploits the active volume of the detector in almost its entirety for the first time, and takes advantage of a reduced radioactive background following the 2011 scintillator purification campaign and of novel analysis tools providing a more precise modeling of the background. Additionally, we set a new limit on the interaction rate of solar hep neutrinos, searched via their elastic scattering on electrons as well as their neutral current-mediated inelastic scattering on carbon, C-12(nu, nu')C-12* (E-gamma = 15.1 MeV).
Публикация
Только метаданные
Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun
(2020) Agostini, M.; Altenmuller, K.; Appel, S.; Atroshchenko, V.; Litvinovich, E.; Machulin, I.; Nugmanov, R.; Skorokhvatov, M.; Литвинович, Евгений Александрович; Мачулин, Игорь Николаевич; Скорохватов, Михаил Дмитриевич
© 2020, The Author(s), under exclusive licence to Springer Nature Limited.For most of their existence, stars are fuelled by the fusion of hydrogen into helium. Fusion proceeds via two processes that are well understood theoretically: the proton–proton (pp) chain and the carbon–nitrogen–oxygen (CNO) cycle1,2. Neutrinos that are emitted along such fusion processes in the solar core are the only direct probe of the deep interior of the Sun. A complete spectroscopic study of neutrinos from the pp chain, which produces about 99 per cent of the solar energy, has been performed previously3; however, there has been no reported experimental evidence of the CNO cycle. Here we report the direct observation, with a high statistical significance, of neutrinos produced in the CNO cycle in the Sun. This experimental evidence was obtained using the highly radiopure, large-volume, liquid-scintillator detector of Borexino, an experiment located at the underground Laboratori Nazionali del Gran Sasso in Italy. The main experimental challenge was to identify the excess signal—only a few counts per day above the background per 100 tonnes of target—that is attributed to interactions of the CNO neutrinos. Advances in the thermal stabilization of the detector over the last five years enabled us to develop a method to constrain the rate of bismuth-210 contaminating the scintillator. In the CNO cycle, the fusion of hydrogen is catalysed by carbon, nitrogen and oxygen, and so its rate—as well as the flux of emitted CNO neutrinos—depends directly on the abundance of these elements in the solar core. This result therefore paves the way towards a direct measurement of the solar metallicity using CNO neutrinos. Our findings quantify the relative contribution of CNO fusion in the Sun to be of the order of 1 per cent; however, in massive stars, this is the dominant process of energy production. This work provides experimental evidence of the primary mechanism for the stellar conversion of hydrogen into helium in the Universe.
Организационные подразделения
Организационная единица
Институт ядерной физики и технологий
Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.
Описание
Эксперимент Borexino (Борекси́но) — эксперимент физики элементарных частиц, нацеленный на изучение низкоэнергетических (~860 кэВ) солнечных нейтрино, рождающихся на Солнце в результате одной из реакций протон-протонного цикла. Эксперимент позволяет глубже понять процессы, происходящие в ядре Солнца, а также помогает определить параметры нейтринных осцилляций. Проект также в состоянии обнаруживать нейтрино от сверхновых звезд в нашей Галактике. Сам детектор расположен в Национальной лаборатории Гран-Сассо (Laboratori Nazionali del Gran Sasso), находящейся в районе города Л'Аквила, Италия. В эксперименте принимают участие исследователи из Италии, США, Германии, Франции, России, Польши и Украины [1]. Детектор начал измерения 16 мая 2007 г., а первые данные в рамках данного проекта были опубликованы 16 августа 2007 года[1]. Эксперимент финансируется несколькими национальными учреждениями, в том числе INFN (Италия) и NSF (США).