M. Agostini

Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76

The GERDA experiment searches for the neutrinoless double beta decay of 76Ge using high-purity germanium detectors enriched in 76Ge. The analysis of the signal time structure provides a powerful tool to identify neutrinoless double beta decay events and to discriminate them from gamma-ray induced backgrounds. Enhanced pulse shape discrimination capabilities of Broad Energy Germanium detectors with a small read-out electrode have been recently reported. This paper describes the full simulation of the response of such a detector, including the Monte Carlo modeling of radiation interaction and subsequent signal shape calculation. A pulse shape discrimination method based on the ratio between the maximum current signal amplitude and the event energy applied to the simulated data shows quantitative agreement with the experimental data acquired with calibration sources. The simulation has been used to study the survival probabilities of the decays which occur inside the detector volume and are difficult to assess experimentally. Such internal decay events are produced by the cosmogenic radio-isotopes 68Ge and 60Co and the neutrinoless double beta decay of 76Ge. Fixing the experimental acceptance of the double escape peak of the 2.614 MeV photon to 90%, the estimated survival probabilities at Qββ = 2.039 MeV are (86±3)% for 76Ge neutrinoless double beta decays, (4.5±0.3)% for the 68Ge daughter 68Ga, and (0.9+0.4−0.2)% for 60Co decays.

Measurement of Solar pp-neutrino flux with Borexino: results and implications

Measurement of the Solar pp-neutrino flux completed the measurement of Solar neutrino fluxes from the pp-chain of reactions in Borexino experiment. The result is in agreement with the prediction of the Standard Solar Model and the MSW/LMA oscillation scenario. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 10(5) years time scale, and sets a strong limit on the power production by the unknown energy sources in the Sun.

Measurement of neutrino flux from the primary proton–proton fusion process in the Sun with Borexino detector

Neutrino produced in a chain of nuclear reactions in the Sun starting from the fusion of two protons, for the first time has been detected in a real-time detector in spectrometric mode. The unique properties of the Borexino detector provided an oppurtunity to disentangle pp-neutrino spectrum from the background components. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 105 years time scale, and sets a strong limit on the power production in the unknown energy sources in the Sun of no more than 4% of the total energy production at 90% C.L.

High significance measurement of the terrestrial neutrino flux with the Borexino detector

We review the geoneutrino measurement with Borexino from 2056 days of data taking. 1. Borexino and Geoneutrinos Borexino is an unsegmented massive liquid scintillator detector installed in the Gran Sasso underground Laboratory (Italy). Borexino has been collecting data since May 2007. The active mass in Borexino consists of 280 tons of organic liquid scintillator, pseudocumene (PC; C9H12) with the addition of PPO at 1.5 g/l [1]. The liquid scintillator is contained within a 100 μm thick nylon transparent vessel 4.25 m in radius. 2212 8-inch photomultipliers (PMTs) are installed on a Stainless Steel Sphere (SSS) which contains the liquid scintillator and about 900 tons of pseudocumene buffer with the addition of a light quencher (DMP) [2]. The SSS is built inside a water Cherenkov detector for vetoing muons and muon related events [3]. The water tank also serves as shielding against neutrons from the underground environment. For each event inside the active mass the energy and the time distribution of hit PMTs are measured. Borexino is a high radio purity detector: all materials were carefully selected. A number of purification campaigns were performed to reduce the intrinsic background, namely 238U, 232Th, 210Pb, 210Po, 222Rn and 85Kr. In Borexino calibrations [4] with radioactive sources have been performed. These calibrations allowed to accurately determine the energy scale and to study the uniformity of the light response [5]. Due to the high level of radio purity, Borexino is also an excellent detector for electron anti-neutrinos. These neutrinos are detected by the so-called inverse-beta decay reaction:

Overview and accomplishments of the Borexino experiment

The Borexino experiment is running at the Laboratori del Gran Sasso in Italy since 2007. Its technical distinctive feature is the unprecedented ultralow background of the inner scintillating core, which is the basis of the outstanding achievements accumulated by the experiment. In this talk, after recalling the main features of the detector, the impressive solar data gathered so far by the experiment will be summarized, with special emphasis to the most recent and prominent result concerning the detection of the fundamental pp solar neutrino flux, which is the direct probe of the engine mechanism powering our star. Such a milestone measurement puts Borexino in the unique situation of being the only experiment able to do solar neutrino spectroscopy over the entire solar spectrum; the counterpart of this peculiar status in the oscillation interpretation of the data is the capability of Borexino alone to perform the full validation across the solar energy range of the MSW-LMA paradigm. The talk will be concluded highlighting the perspectives for the final stage of the solar program of the experiment, centered on the goal to fully complete the solar spectroscopy with the missing piece of the CNO neutrinos. If successful, such a measurement would represent the final crowning of the long quest of Borexino to unravel all the properties of the neutrinos from the Sun.

Recent results from Borexino

We review the solar neutrinos results of Borexino and the limit on the charge conservation obtained in the context of the analysis of the low energy region of the energy spectrum.

Borexino: Recent results and future plans

Borexino is continuing to take data and presenting the new results. The most recent Borexino results are discussed and plans for the nearest future are presented.

Test of the electron stability with the Borexino detector

Despite the fact that the electric charge conservation law is confirmed by many experiments, search for its possible violation remains a way of searching for physics beyond the Standard Model. Experimental searches for the electric charge non-conservation mainly consider electron decays into neutral particles. The Borexino experiment is an excellent tool for the electron decay search due to the highest radiopurity among all the existing experiments, large detector mass, and good sensitivity at low energies. The process considered in this study is a decay into a photon and a neutrino, for which a new lower limit on the electron lifetime is obtained. This is the best electron lifetime limit up to date, exceeding the previous one obtained at the Borexino prototype at two orders of magnitude.

CNO and pep solar neutrino measurements and perspectives in Borexino

The detection of neutrinos emitted in the CNO reactions in the Sun is one of the ambitious goals of Borexino Phase-II. A measurement of CNO neutrinos would be a milestone in astrophysics, and would allow to solve serious issues in current solar models. A precise measurement of the rate of neutrinos from the pep reaction would allow to investigate neutrino oscillations in the MSW transition region. The pep and CNO solar neutrino physics, the measurement in Borexino Phase-I and the perspectives for the new phase are reviewed in this proceeding.

Borexino: from the Sun to the Earth

M. Agostini, K. Altenmuller, S. Appel, G. Bellini, J. Benziger, D. Bick, G. Bonfini, D. Bravo, B. Caccianiga, F. Calaprice, A. Caminata, P. Cavalcante, A. Chepurnov, D. D’Angelo, S. Davini, A. Derbin, L. di Noto, I. Drachnev, A. Empl, A. Etenko, K. Fomenko, D. Franco, F. Gabriele, C. Galbiati, C. Ghiano, M. Giammarchi, M. Goger-Neff, A. Goretti, M. Gromov, C. Hagner, E. Hungerford, Aldo Ianni, Andrea Ianni, K. Jedrzejczak, M. Kaiser, V. Kobychev, D. Korablev, G. Korga, D. Kryn, M. Laubenstein, B. Lehnert, E. Litvinovich, F. Lombardi, P. Lombardi, L. Ludhova, G. Lukyanchenko, I. Machulin, S. Manecki, W. Maneschg, S. Marcocci, E. Meroni, M. Meyer, L. Miramonti, M. Misiaszek, M. Montuschi, P. Mosteiro, V. Muratova, B. Neumair, L. Oberauer, M. Obolensky, F. Ortica, K. Otis, L. Pagani, M. Pallavicini, L. Papp, L. Perasso, A. Pocar, G. Ranucci, A. Razeto, A. Re, A. Romani, R. Roncin, N. Rossi, S. Schonert, D. Semenov, H. Simgen, M. Skorokhvatov, O. Smirnov, A. Sotnikov, S. Sukhotin, Y. Suvorov, R. Tartaglia, G. Testera, J. Thurn, M. Toropova, E. Unzhakov, R.B. Vogelaar, F. von Feilitzsch, H. Wang, J. Winter, M. Wojcik, M. Wurm, Z. Yokley, O. Zaimidoroga, S. Zavatarelli, K. Zuber, G. Zuzel