Direct Measurement of theBe7Solar Neutrino Flux with 192 Days of Borexino Data

Abstract

We report the direct measurement of the 7 Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV 7 Be neutrinos is 49±3stat±4syst counts/(day·100 ton). The hypothesis of no oscillation for 7 Be solar neutrinos is inconsistent with our measurement at the 4σ C.L.. Our result is the first direct measurement of the survival probability for solar νe in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of 7 Be, pp, and CNO solar νe, and the limit on the magnetic moment of neutrinos.PACS numbers: 13.35. Hb, 14.60.St, 26.65.+t, 95.55.Vj, 29.40.Mc Neutrino oscillations [1] are the established mechanism to explain the solar neutrino problem, which originated from observations in radiochemical experiments with a sub-MeV threshold [2,3] and from real time observation of high energy neutrinos [4,5]. Neutrino oscillations were also observed in atmospheric neutrinos [4] and have been confirmed with observation of reactorν e [6]. Borexino is the first experiment to report a real-time observation arXiv:0805.3843v2 [astro-ph]

A Search for Low-energy Neutrinos Correlated with Gravitational Wave Events GW 150914, GW 151226, and GW 170104 with the Borexino Detector

“…A detailed description of the detector could be found elsewhere [17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses

“…in particle or cosmic-ray physics. The largest liquid scintillation detector recently constructed is the Borexino detector (Arpesella et al 2008) located in the Gran Sasso underground laboratory (~3500 m w.e.). The Borexino experiment aims to measure low-energy solar neutrinos in real time by elastic neutrino-electron scattering.…”

New limits on neutrino magnetic moment through nonvanishing 13-mixing

“…[16] to include Phase-II solar neutrino data, and quoted distinct limits for different magnetic moments terms, which can be directly compared with ours. The limit on the effective magnetic moment is μ eff < 2.8 × 10 −11 μ B whichusing the best-fit points for oscillation parameters-can be translated to individual limits on μ ij by the relation [21] …”

“…For instance, the GEMMA experiment [14]-which uses a reactor antineutrino flux and analyzes the recoil electron spectra produced from the detection of such an antineutrino flux-has established the limit μ ν < 2.9 × 10 −11 μ B . The experiments Super-Kamiokande [15] and Borexino [16] obtained limits of μ ν < 1.1 × 10 −10 μ B and μ ν < 5.4 × 10 −11 μ B , respectively, by analyzing the spectrum of the solar neutrino flux, which applies for a combination of all neutrino magnetic moment elements. Analyses of such limits in conjunction with different sets of data can be found in Refs.…”