Borexino, a real-time device for low energy neutrino spectroscopy is nearing completion of construction in the underground laboratories at Gran Sasso, Italy (LNGS). The experiment's goal is the ...direct measurement of the flux of
7
Be solar neutrinos of all flavors via neutrino–electron scattering in an ultra-pure scintillation liquid. Seeded by a series of innovations which were brought to fruition by large-scale operation of a 4-ton test detector at LNGS, a new technology has been developed for Borexino. It enables sub-MeV solar neutrino spectroscopy for the first time. This paper describes the design of Borexino, the various facilities essential to its operation, its spectroscopic and background suppression capabilities and a prognosis of the impact of its results towards resolving the solar neutrino problem. Borexino will also address several other frontier questions in particle physics, astrophysics and geophysics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The techniques researched, developed and applied towards the measurement of radioisotope concentrations at ultra-low 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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Pauli exclusion principle (PEP) has been tested for nucleons (n,p) in \({}^{12}{\rm C}\) and \({}^{16}{\rm O}\) nuclei, using the results of background measurements with the prototype of the ...Borexino detector, the Counting Test Facility (CTF). The approach consisted of a search for \(\gamma\), n, p and/or \(\alpha\)’s emitted in a non-Paulian transition of 1P- shell nucleons to the filled 1S1/2 shell in nuclei. Similarly, the Pauli-forbidden \(\beta^{\pm}\) decay processes were searched for. Due to the extremely low background and the large mass (4.2 tons) of the CTF detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established: \(\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde C} + \gamma) > 2.1\cdot10^{27} \mathrm y\), \(\tau({}^{12}{\rm C} \rightarrow {}^{11}{\rm\widetilde B} + p) > 5.0\cdot10^{26} {\mathrm{y}}\), \(\tau({}^{12}{\rm C} ({}^{16}{\rm O}) \rightarrow {}^{11}{\rm\widetilde C} ({}^{15}{\rm\widetilde O} ) + n) > 3.7 \cdot 10^{26} {\mathrm{y}}\), \(\tau({}^{12}{\rm C} \rightarrow {}^{8}{\rm\widetilde{Be}} + \alpha) > 6.1 \cdot 10^{23} \mathrm y\), \(\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde N} + e^- + \widetilde{\nu_e}) > 7.6 \cdot 10^{27} \mathrm y\) and \(\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde B} + e^ + + \nu_e) > 7.7 \cdot 10^{27} \mathrm y\), all at \(90 \%\) C.L.
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DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The results of background measurements with the second version of the BOREXINO Counting Test Facility (CTF-II), installed in the Gran Sasso Underground Laboratory, were used to obtain limits on the ...instability of nucleons, bounded in nuclei, for decays into invisible channels (inv): disappearance, decays to neutrinos, etc. The approach consisted of a search for decays of unstable nuclides resulting from N and NN decays of parent 12C, 13C and 16O nuclei in the liquid scintillator and the water shield of the CTF. Due to the extremely low background and the large mass (4.2 t) of the CTF detector, the most stringent (or competitive) up-to-date experimental bounds have been established: τ(n→inv)>1.8×1025 yr, τ(p→inv)>1.1×1026 yr, τ(nn→inv)>4.9×1025 yr and τ(pp→inv)>5.0×1025 yr, all at 90% C.L.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report the direct measurement of the {sup 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 ...{sup 7}Be neutrinos is 49{+-}3{sub stat}{+-}4{sub syst} counts/(day{center_dot}100 ton). The hypothesis of no oscillation for {sup 7}Be solar neutrinos is inconsistent with our measurement at the 4{sigma} C.L. Our result is the first direct measurement of the survival probability for solar {nu}{sub e} in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of {sup 7}Be, pp, and CNO solar {nu}{sub e}, and the limit on the effective neutrino magnetic moment using solar neutrinos.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
We report the direct measurement of the 7Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV 7Be ...neutrinos is 49+/-3stat+/-4syst counts/(day.100 ton). The hypothesis of no oscillation for 7Be solar neutrinos is inconsistent with our measurement at the 4sigma C.L. Our result is the first direct measurement of the survival probability for solar nu(e) in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of 7Be, pp, and CNO solar nu(e), and the limit on the effective neutrino magnetic moment using solar neutrinos.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The prototype of the Borexino detector Counting Test Facility, located in the Gran-Sasso laboratory, has been used to obtain a bound on the stability of the electron. The new lower limit on the mean ...lifetime defined on 32.1 days of data set is τ(e−→νe+γ)⩾4.6×1026 yr (90% c.l.).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The results of background measurements with the prototype of the Borexino detector (CTF) have been used to obtain an upper bound on the neutrino magnetic moment, μν. The new upper limit for μν from ...pp and 7Be solar neutrinos is (5.5×10−10)μB (90% c.l.) in the Standard Solar Model scenario. This is the first limit on μν obtained using sub-MeV neutrinos. The sensitivity of the prototype to the neutrino charge radius and the neutrino radiative decay are also presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report the direct measurement of the 7Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV 7Be ...neutrinos is 49±3stat±4syst counts/(day·100 ton). The hypothesis of no oscillation for 7Be 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 7Be, pp, and CNO solar νe, and the limit on the effective neutrino magnetic moment using solar neutrinos.
Experiments in
sub-MeV particle astrophysics pose stringent requirements on the radioactive background. During the development of
borexino major progress was achieved in the reduction and ...determination of the background, especially that due to
226Ra and
222Rn. Employing charcoal adsorption and internal proportional counting
222Rn activities in the range of 50 μ
Bq are routinely detected. Solid, liquid or gaseous samples as well as large volumes in the detector periphery are analysed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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