F. Lombardi

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

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.

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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Search for Solar Axions Produced in p(d,3He)A Reaction with Borexino Detector

source experiments in Borexino and shows the expected sensitivity to eV mass sterile neutrinos for three possible different phases of the experiment. Expected results on neutrino magnetic moment, electroweak mixing angle, and couplings to axial and vector currents are shown too.

Borexino calibrations: Hardware, Methods, and Results

Borexino, a liquid scintillator detector at LNGS, is designed for the detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear reactors, and the Earth. The feeble nature of these signals requires a strong suppression of backgrounds below a few MeV. Very low intrinsic radiogenic contamination of all detector components needs to be accompanied by the efficient identification of muons and of muon-induced backgrounds. Muons produce unstable nuclei by spallation processes along their trajectory through the detector whose decays can mimic the expected signals; for isotopes with half-lives longer than a few seconds, the dead time induced by a muon-related veto becomes unacceptably long, unless its application can be restricted to a sub-volume along the muon track. Consequently, not only the identification of muons with very high efficiency but also a precise reconstruction of their tracks is of primary importance for the physics program of the experiment. The Borexino inner detector is surrounded by an outer water-Cherenkov detector that plays a fundamental role in accomplishing this task. The detector design principles and their implementation are described. The strategies adopted to identify muons are reviewed and their efficiency is evaluated. The overall muon veto efficiency is found to be 99.992 % or better. Ad-hoc track reconstruction algorithms developed are presented. Their performance is tested against muon events of known direction such as those from the CNGS neutrino beam, test tracks available from a dedicated External Muon Tracker and cosmic muons whose angular distribution reflects the local overburden profile. The achieved angular resolution is ~ 3?-5? and the lateral resolution is ~ 35-50 cm, depending on the impact parameter of the crossing muon. The methods implemented to efficiently tag cosmogenic neutrons are also presented.

New limits on heavy sterile neutrino mixing in 8B decay obtained with the Borexino detector

We have measured the muon flux at the underground Gran Sasso National Laboratory (3800 m w.e.) to be (3.41 \pm 0.01) \times 10-4m-2s-1 using four years of Borexino data. A modulation of this signal is observed with a period of (366\pm3) days and a relative amplitude of (1.29 \pm 0.07)%. The measured phase is (179 \pm 6) days, corresponding to a maximum on the 28th of June. Using the most complete atmospheric data models available, muon rate fluctuations are shown to be positively correlated with atmospheric temperature, with an effective coefficient {\alpha}T = 0.93 \pm 0.04. This result represents the most precise study of the muon flux modulation for this site and is in good agreement with expectations.

Solar neutrino with Borexino: Results and perspectives

The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Yn = (3.10?0.11)?10?4?n/(??(g/cm2)). The distance profile between the parent muon track and the neutron capture point has the average value ? = (81.5?2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for 12N, 12B, 8He, 9C, 9Li, 8B, 6He, 8Li, 11Be, 10C and 11C. All results are compared with Monte Carlo simulation predictions using the FLUKA and GEANT4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being 11C yield for which both codes return about 50% lower values. The predicted ?-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.