The rate of neutrino-electron elastic scattering interactions from 862 keV (7)Be solar neutrinos in Borexino is determined to be 46.0±1.5(stat)(-1.6)(+1.5)(syst) counts/(day·100 ton). This ...corresponds to a ν(e)-equivalent (7)Be solar neutrino flux of (3.10±0.15)×10(9) cm(-2) s(-1) and, under the assumption of ν(e) transition to other active neutrino flavours, yields an electron neutrino survival probability of 0.51±0.07 at 862 keV. The no flavor change hypothesis is ruled out at 5.0 σ. A global solar neutrino analysis with free fluxes determines Φ(pp)=6.06(-0.06)(+0.02)×10(10) cm(-2) s(-1) and Φ(CNO)<1.3×10(9) cm(-2) s(-1) (95% C.L.). These results significantly improve the precision with which the Mikheyev-Smirnov-Wolfenstein large mixing angle neutrino oscillation model is experimentally tested at low energy.
We have studied the
α
-decays of
214
Po into
210
Pb and of
212
Po into
208
Pb tagged by the coincidence with the preceding
β
-decays from
214
Bi and
212
Bi, respectively. The
222
Rn,
232
Th, and
220
...Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of
214
Po is (236.00 ± 0.42(stat) ± 0.15(syst))
μ
s and that of
212
Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.
Geo-neutrinos and Borexino Ludhova, L.; Bellini, G.; Benziger, J. ...
Physics of particles and nuclei,
03/2015, Letnik:
46, Številka:
2
Journal Article
Recenzirano
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. After a brief introduction ...about the Earth, the geo-neutrinos’ properties and the main aims of their study are discussed. An overview of the latest experimental results obtained by the Borexino collaboration is provided, followed by a short overview of future perspectives of this new inter-disciplinary field.
Solar neutrinos have been pivotal to the discovery of neutrino flavour oscillations and are a unique tool to probe the reactions that keep the Sun shine. Although most of solar neutrino components ...have been directly measured, the neutrinos emitted by the keystone pp reaction, in which two protons fuse to make a deuteron, have so far eluded direct detection. The Borexino experiment, an ultra–pure liquid scintillator detector running at the Laboratori Nazionali del Gran Sasso in Italy, has now filled the gap, providing the first direct real time measurement of pp neutrinos and of the solar neutrino luminosity.
We report the measurement of ν-e elastic scattering from B8 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 0.22±0.04(stat)±0.01(syst)cpd/100t, which corresponds to ΦB8ES=2.4±0.4±0.1×106cm-2s-1, in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the B8 neutrino flux predicted by the high metallicity standard solar model, the average B8 νe survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for Be7 and B8 neutrinos as measured by Borexino differ by 1.9σ. 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.
We observed, for the first time, solar neutrinos in the 1.0–1.5 MeV energy range. We determined the rate of pep solar neutrino interactions in Borexino to be 3.l±0.6stat±0.3syst counts/(day-100 ton). ...Assuming the pep neutrino flux predicted by the Standard Solar Model, we obtained a constraint on the CNO solar neutrino interaction rate of <7.9 counts/(day-100 ton) (95% C.L.). The absence of the solar neutrino signal is disfavored at 99.97% C.L., while the absence of the pep signal is disfavored at 98% C.L. The necessary sensitivity was achieved by adopting data analysis techniques for the rejection of cosmogenic 11C, the dominant background in the 1-2 MeV region. Assuming the MSW-LMA solution to solar neutrino oscillations, these values correspond to solar neutrino fluxes of (1.6±0.3)×l08cm−2s−1 and <7.7×l08 cm−2s−1 (95% C.L.), respectively, in agreement with both the High and Low Metallicity Standard Solar Models. These results represent the first direct evidence of the pep neutrino signal and the strongest constraint of the CNO solar neutrino flux to date.
Spectroscopy of solar neutrinos Wurm, M.; von Feilitzsch, F.; Göger-Neff, M. ...
Astronomische Nachrichten,
20/May , Letnik:
331, Številka:
5
Journal Article
The recent successes in neutrino physics prove that liquid-scintillator detectors allow to combine high energy resolution, efficient means of background reduction, and a large detection volume. In ...the planned LENA (Low Energy Neutrino Astronomy) experiment, a target mass of 50 kt will enable the investigation of a variety of terrestrial and astrophysical neutrino sources. The high-statistics spectroscopy of geoneutrinos, solar neutrinos and supernova neutrinos will provide new insights in the heat production processes of Earth and Sun, and the workings of a gravitational collapse. The same measurements will as well investigate neutrino properties as oscillation parameters and mass hierarchy. A first spectroscopic measurement of the low flux of diffuse supernova neutrino background is within the sensitivity of the LENA detector. Finally, a life-time limit of several 1034 years can be set to the proton decay into proton and anti-neutrino, testing the predictions of SUSY theory. The present contribution includes a review of the scientific studies that were performed in the last years as well as a report on currently on-going R&D activities.
Borexino, a large volume liquid scintillator detector installed at Gran Sasso laboratory, demonstrated extraordinary sensitivity with respect to neutrino and antineutrino detection, reporting the ...best up to date results on low energy solar neutrino fluxes and performing geo-neutrino detection. Energy and position of 1 MeV events in Borexino are recon- structed with a precision of 5% and 14cm respectively. These performances together with extremely low background provides an excellent opportunity for the study of short distance neutrino oscillations on the eV mass scale with artificial neutrino sources.
The possible layouts for 51Cr (monoenergetic neutrino) and 144Ce–144Pr (antineutrino from β-decay) source experiments in Borexino and the expected sensitivity to sterile neutrinos for three possible designs of the experiment are presented.
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