F. Calaprice

First evidence of pep solar neutrinos by direct detection in Borexino.

G. Bellini, J. Benziger, D. Bick, S. Bonetti, G. Bonfini, D. Bravo, M. Buizza Avanzini, B. Caccianiga, L. Cadonati, F. Calaprice, C. Carraro, P. Cavalcante, A. Chavarria, D. D’Angelo, S. Davini, A. Derbin, A. Etenko, K. Fomenko, 4 D. Franco, C. Galbiati, S. Gazzana, C. Ghiano, M. Giammarchi, M. Goeger-Neff, A. Goretti, L. Grandi, E. Guardincerri, S. Hardy, Aldo Ianni, Andrea Ianni, D. Korablev, G. Korga, Y. Koshio, D. Kryn, M. Laubenstein, T. Lewke, E. Litvinovich, B. Loer, F. Lombardi, P. Lombardi, L. Ludhova, I. Machulin, S. Manecki, W. Maneschg, G. Manuzio, Q. Meindl, E. Meroni, L. Miramonti, M. Misiaszek, 4 D. Montanari, 7 P. Mosteiro, V. Muratova, L. Oberauer, M. Obolensky, F. Ortica, K. Otis, M. Pallavicini, L. Papp, L. Perasso, S. Perasso, A. Pocar, J. Quirk, R.S. Raghavan, G. Ranucci, A. Razeto, A. Re, A. Romani, A. Sabelnikov, R. Saldanha, C. Salvo, S. Schönert, H. Simgen, M. Skorokhvatov, O. Smirnov, A. Sotnikov, S. Sukhotin, Y. Suvorov, R. Tartaglia, G. Testera, D. Vignaud, R.B. Vogelaar, F. von Feilitzsch, J. Winter, M. Wojcik, A. Wright, M. Wurm, J. Xu, O. Zaimidoroga, S. Zavatarelli, and G. Zuzel

Science and technology of Borexino: a real-time detector for low energy solar neutrinos

Abstract 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 experiments 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.

Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector

G. Bellini, J. Benziger, S. Bonetti, M. Buizza Avanzini, B. Caccianiga, L. Cadonati, F. Calaprice, C. Carraro, A. Chavarria, A. Chepurnov, F. Dalnoki-Veress, D. D’Angelo, S. Davini, H. de Kerret, A. Derbin, A. Etenko, K. Fomenko, D. Franco, C. Galbiati, S. Gazzana, C. Ghiano, M. Giammarchi, M. Goeger-Neff, A. Goretti, E. Guardincerri, S. Hardy, Aldo Ianni, Andrea Ianni, M. Joyce, G. Korga, D. Kryn, M. Laubenstein, M. Leung, T. Lewke, E. Litvinovich, B. Loer, P. Lombardi, L. Ludhova, I. Machulin, S. Manecki, W. Maneschg, G. Manuzio, Q. Meindl, E. Meroni, L. Miramonti, M. Misiaszek, 11 D. Montanari, V. Muratova, L. Oberauer, M. Obolensky, F. Ortica, M. Pallavicini, L. Papp, L. Perasso, S. Perasso, A. Pocar, R.S. Raghavan, G. Ranucci, A. Razeto, A. Re, P. Risso, A. Romani, D. Rountree, A. Sabelnikov, R. Saldanha, C. Salvo, S. Schönert, H. Simgen, M. Skorokhvatov, O. Smirnov, A. Sotnikov, S. Sukhotin, Y. Suvorov, 9 R. Tartaglia, G. Testera, D. Vignaud, R.B. Vogelaar, F. von Feilitzsch, J. Winter, M. Wojcik, A. Wright, M. Wurm, J. Xu, O. Zaimidoroga, S. Zavatarelli, and G. Zuzel

Observation of Geo{Neutrinos

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 −3.4( +14.6 −8.2 ) geo–neutrino events, with errors corresponding to a 68.3% (99.73%) C.L. From the lnL 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 −1.3( +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.

Measurement of the 14C abundance in a low-background liquid scintillator

Abstract The 14 C/ 12 C ratio in 4.8 m 3 of high-purity liquid scintillator was measured at (1.94±0.09)×10 −18 , the lowest 14 C abundance ever measured. At this level the spectroscopy of low-energy solar neutrinos, in particular a measurement of the 7 Be neutrino flux, will not be obstructed by the 14 C β decay intrinsic to a liquid scintillator detector. A comprehensive study of the deviation of the shape of the 14 C β spectrum from the allowed statistical shape reveals consistent results with recent observations and calculations. Possible origins of the 14 C in the liquid scintillator are discussed.

Measurement of geo-neutrinos from 1353 days of Borexino

Abstract We present a measurement of the geo-neutrino signal obtained from 1353 days of data with the Borexino detector at Laboratori Nazionali del Gran Sasso in Italy. With a fiducial exposure of ( 3.69 ± 0.16 ) × 10 31 proton × year after all selection cuts and background subtraction, we detected ( 14.3 ± 4.4 ) geo-neutrino events assuming a fixed chondritic mass Th/U ratio of 3.9. This corresponds to a geo-neutrino signal S geo = ( 38.8 ± 12.0 ) TNU with just a 6 × 10 − 6 probability for a null geo-neutrino measurement. With U and Th left as free parameters in the fit, the relative signals are S Th = ( 10.6 ± 12.7 ) TNU and S U = ( 26.5 ± 19.5 ) TNU . Borexino data alone are compatible with a mantle geo-neutrino signal of ( 15.4 ± 12.3 ) TNU , while a combined analysis with the KamLAND data allows to extract a mantle signal of ( 14.1 ± 8.1 ) TNU . Our measurement of 31.2 − 6.1 + 7.0 reactor anti-neutrino events is in agreement with expectations in the presence of neutrino oscillations.

Effects of Nitrogen contamination in liquid Argon

A dedicated test of the effects of Nitrogen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. A detector has been designed and assembled for this specific task and connected to a system for the injection of controlled amounts of gaseous Nitrogen into the liquid Argon. The purpose of the test is to detect the reduction of the Ar scintillation light emission as a function of the amount of the Nitrogen contaminant injected in the Argon volume. A wide concentration range, spanning from ~ 10?1 ppm up to ~ 103 ppm, has been explored. Measurements have been done with electrons in the energy range of minimum ionizing particles (?-conversion from radioactive sources). Source spectra at different Nitrogen contaminations are analyzed, showing sensitive reduction of the scintillation yield at increasing concentrations. Direct PMT signal acquisition exploiting high time resolution by fast waveform recording allowed high precision extraction of the main characteristics of the scintillation light emission in contaminated LAr. In particular, the decreasing behavior in lifetime and relative amplitude of the slow component is found to be appreciable starting from (1 ppm) of Nitrogen concentrations. The rate constant of the quenching process induced by Nitrogen in liquid Ar has been found to be kQ(N2) = 0.11 ? 0.01 ?s?1ppm?1, consistent with a previous measurement of this quantity but with significant improvement in precision. On the other hand, no evidence for absorption by N2 impurities has been found up to the higher concentrations here explored.

SOX: Short distance neutrino Oscillations with BoreXino

A bstractThe 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 (νe) and 144Ce-144Pr

Cosmic-muon flux and annual modulation in Borexino at 3800 m water-equivalent depth

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