Search

The search for neutrino events in correlation with gravitational wave (GW) events for three observing runs (O1, O2 and O3) from 09/2015 to 03/2020 has been performed using the Borexino data-set of the same period. We have searched for signals of neutrino-electron scattering and inverse beta-decay (IBD) within a time window of ± 1000 s centered at the detection moment of a particular GW event. The search was done with three visible energy thresholds of 0.25, 0.8 and 3.0 MeV. Two types of incoming neutrino spectra were considered: the mono-energetic line and the supernova-like spectrum. GW candidates originated by merging binaries of black holes (BHBH), neutron stars (NSNS) and neutron star and black hole (NSBH) were analyzed separately. Additionally, the subset of most intensive BHBH mergers at closer distances and with larger radiative mass than the rest was considered. In total, follow-ups of 74 out of 93 gravitational waves reported in the GWTC-3 catalog were analyzed and no statistically significant excess over the background was observed. As a result, the strongest upper limits on GW-associated neutrino and antineutrino fluences for all flavors ( ν e , ν μ , ν τ ) at the level 10 9 - 10 15 cm - 2 GW - 1 have been obtained in the 0.5–5 MeV neutrino energy range. [ABSTRACT FROM AUTHOR]

Stars are fuelled by the fusion of hydrogen into helium via two processes: the "pp chain" and the "CNO cycle." Neutrinos emitted in the core of the Sun are the only direct probe for the investigation of such processes. The Borexino experiment has performed a complete spectroscopy of the neutrinos from the "pp chain," and has recently reported the first experimental evidence of neutrinos from the CNO cycle, never observed before, being this process subdominant in the Sun (about 1% of the solar energy). This experimental evidence of the CNO neutrinos was obtained using the highly radiopure large-volume liquid-scintillator detector of Borexino. Advances in the thermal stabilization of the detector over the last five years enabled us to exploit a method to constrain the rate of Bi-210 contaminating the scintillator, the main background for such a measurement. Since the CNO cycle is dominant in massive starts, this result proves the evidence of the primary mechanism for the stellar conversion of hydrogen into helium in the Universe. [ABSTRACT FROM AUTHOR]

The search for neutrino events in correlation with 42 most intense fast radio bursts (FRBs) has been performed using the Borexino dataset from 05/2007 to 06/2021. We have searched for signals with visible energies above 250 keV within a time window of ± 1000 s corresponding to detection time of a particular FRB. We also applied an alternative approach based on searching for specific shapes of neutrino-electron scattering spectra in the full exposure data of the Borexino detector. In particular, two incoming neutrino spectra were considered: the monoenergetic line and the spectrum expected from supernovae. The same spectra were considered for electron antineutrinos detected through inverse beta-decay reaction. No statistically significant excess over the background was observed. As a result, the strongest upper limits on FRB-associated neutrino fluences of all flavors have been obtained in the 0.5–50 MeV neutrino energy range. [ABSTRACT FROM AUTHOR]

Cosmogenic radio-nuclei are an important source of background for low-energy neutrino experiments. In Borexino, cosmogenic 11 C decays outnumber solar pep and CNO neutrino events by about ten to one. In order to extract the flux of these two neutrino species, a highly efficient identification of this background is mandatory. We present here the details of the most consolidated strategy, used throughout Borexino solar neutrino measurements. It hinges upon finding the space-time correlations between 11 C decays, the preceding parent muons and the accompanying neutrons. This article describes the working principles and evaluates the performance of this Three-Fold Coincidence (TFC) technique in its two current implementations: a hard-cut and a likelihood-based approach. Both show stable performances throughout Borexino Phases II (2012–2016) and III (2016–2020) data sets, with a 11 C tagging efficiency of ∼ 90 % and ∼ 63–66 % of the exposure surviving the tagging. We present also a novel technique that targets specifically 11 C produced in high-multiplicity during major spallation events. Such 11 C appear as a burst of events, whose space-time correlation can be exploited. Burst identification can be combined with the TFC to obtain about the same tagging efficiency of ∼ 90 % but with a higher fraction of the exposure surviving, in the range of ∼ 66–68 %. [ABSTRACT FROM AUTHOR]

The cosmic silence of the underground Gran Sasso laboratory together with the exceptional radio purity of the liquid scintillator, has allowed Borexino to investigate the radiogenic heating of the Earth's interior and to contribute to various fields of experimental neutrino astronomy. This contribution is aimed to summarize the results obtained by Borexino on geo-neutrinos and on possible extra-terrestrial sources of antineutrinos such as supernovae explosions and solar flares. [ABSTRACT FROM AUTHOR]

Neutrinos emitted in the carbon, nitrogen, oxygen (CNO) fusion cycle in the Sun are a sub-dominant, yet crucial component of solar neutrinos whose flux has not been measured yet. The Borexino experiment at the Laboratori Nazionali del Gran Sasso (Italy) has a unique opportunity to detect them directly thanks to the detector's radiopurity and the precise understanding of the detector backgrounds. We discuss the sensitivity of Borexino to CNO neutrinos, which is based on the strategies we adopted to constrain the rates of the two most relevant background sources, pep neutrinos from the solar pp-chain and 210 Bi beta decays originating in the intrinsic contamination of the liquid scintillator with 210 Pb. Assuming the CNO flux predicted by the high-metallicity Standard Solar Model and an exposure of 1000 days × 71.3 t, Borexino has a median sensitivity to CNO neutrino higher than 3 σ . With the same hypothesis the expected experimental uncertainty on the CNO neutrino flux is 23%, provided the uncertainty on the independent estimate of the 210 Bi interaction rate is 1.5 cpd / 100 ton . Finally, we evaluated the expected uncertainty of the C and N abundances and the expected discrimination significance between the high and low metallicity Standard Solar Models (HZ and LZ) with future more precise measurement of the CNO solar neutrino flux. [ABSTRACT FROM AUTHOR]

The large-scale polarization explorer (LSPE) is a cosmology program for the measurement of large-scale curl-like features (B-modes) in the polarization of the cosmic microwave background. Its goal is to constrain the background of inflationary gravity waves traveling through the universe at the time of matter-radiation decoupling. The two instruments of LSPE are meant to synergically operate by covering a large portion of the northern microwave sky. LSPE/STRIP is a coherent array of receivers planned to be operated from the Teide Observatory in Tenerife, for the control and characterization of the low-frequency polarized signals of galactic origin; LSPE/SWIPE is a balloon-borne bolometric polarimeter based on 330 large throughput multi-moded detectors, designed to measure the CMB polarization at 150 GHz and to monitor the polarized emission by galactic dust above 200 GHz. The combined performance and the expected level of systematics mitigation will allow LSPE to constrain primordial B-modes down to a tensor/scalar ratio of 10 - 2 . We here report the status of the STRIP pre-commissioning phase and the progress in the characterization of the key subsystems of the SWIPE payload (namely the cryogenic polarization modulation unit and the multi-moded TES pixels) prior to receiver integration. [ABSTRACT FROM AUTHOR]

The Borexino detector measures solar neutrino fluxes via neutrino-electron elastic scattering. Observed spectra are determined by the solar-νe survival probability Pee(E), and the chiral couplings of the neutrino and electron. Some theories of physics beyond the Standard Model postulate the existence of Non-Standard Interactions (NSI’s) which modify the chiral couplings and Pee(E). In this paper, we search for such NSI’s, in particular, flavor-diagonal neutral current interactions that modify the νee and ντe couplings using Borexino Phase II data. Standard Solar Model predictions of the solar neutrino fluxes for both high- and low-metallicity assumptions are considered. No indication of new physics is found at the level of sensitivity of the detector and constraints on the parameters of the NSI’s are placed. In addition, with the same dataset the value of sin2θW is obtained with a precision comparable to that achieved in reactor antineutrino experiments. [ABSTRACT FROM AUTHOR]

The aim of the SOX-Borexino project is to verify or falsify the existence of eV-scale sterile neutrinos. The existence of sterile neutrinos is suspected because of several anomalies, which were observed in previous experiments. A ~3.7 PBq electron antineutrino source made of Ce will be installed below the Borexino detector at LNGS, Italy, to search for short-baseline oscillations of active-to-sterile neutrinos within the detector volume. Source delivery and beginning of data acquisition is planned for end of 2016, preliminary results are expected already in 2017. [ABSTRACT FROM AUTHOR]

The 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 $$ \left( {{{\overline{\nu}}_e}} \right) $$ 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. [ABSTRACT FROM AUTHOR]

We have studied the α-decays of Po into Pb and of Po into Pb tagged by the coincidence with the preceding β-decays from Bi and Bi, respectively. The Rn, Th, and Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements. [ABSTRACT FROM AUTHOR]

Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions emitted in the M1-transitions of 7Li*. The Compton conversion of axion to a photon A+e→e+γ, axioelectric effect A+e+Z→e+Z, decay of axion in two photons A→2γ and Primakoff conversion on nuclei A+Z→γ+Z are considered. The upper limit on constants of interaction of axion with electrons, photons and nucleons – gAegAN≤(1.0–2.4)×10-10 at mA≤450 keV and gAγgAN≤5×10-9 GeV-1 at mA≤10 keV are obtained (90%c.l.). For heavy axions with mass at 100A<400 keV the limits gAe<(0.7–2.0)×10-8 and gAγ<10-9–10-8 are obtained in assumption that gAN depends on mA as for KSVZ axion model. These limits are stronger than obtained in previous laboratory-based experiments using nuclear reactor and artificial radioactive sources. [ABSTRACT FROM AUTHOR]

Electron antineutrino interactions above the inverse beta decay energy of protons (Eν̄e>1.8 MeV) were looked for with the Borexino counting test facility (CTF). One candidate event survived after rejection of background, which included muon-induced neutrons and random coincidences. An upper limit on the solar ν̄e flux, assumed having the 8B solar neutrino energy spectrum, of 1.1×105 cm-2 s-1 (90% C.L.) was set with a 7.8 ton × year exposure. This upper limit corresponds to a solar neutrino transition probability, νe→ν̄e, of 0.02 (90% C.L.). Predictions for antineutrino detection with Borexino, including geoneutrinos, are discussed on the basis of background measurements performed with the CTF. [ABSTRACT FROM AUTHOR]

The Pauli exclusion principle (PEP) has been tested for nucleons (n,p) inandnuclei, 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,n,pand/or’s emitted in a non-Paulian transition of 1P- shell nucleons to the filled 1S1/2 shell in nuclei. Similarly, the Pauli-forbiddendecay 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:,,,,and, all atC.L. [ABSTRACT FROM AUTHOR]

If heavy neutrinos with mass m[sub ν[sub H]] ≥ 2m[sub e] are emitted in the decays of [sup 8]B in the Sun, then ν[sub H] → ν[sub L] + e[sup +] + e[sup –] decays should be observed. In the present work, the results of background measurements with the Borexino Counting Test Facility have been used to obtain bounds on the number of these decays. As a result, new limits on the coupling |U[sub eH]|[sup 2] of a massive neutrino in the range of 1.1 MeV to 12 MeV have been derived (|U[sub eH]|[sup 2] ≤ 10[sup –3]–10[sup –5]). The obtained limits on the mixing parameter are stronger than obtained in previous experiments using nuclear reactors and accelerators. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The unique features (super-low background and large sensitive volume) of the CTF and BOREXINO set ups are used in the CAMEO project for a high sensitivity study of $^{100}$Mo and $^{116}$Cd neutrinoless 2 $\beta $ decay. Pilot measurements with $^{116}$Cd and Monte Carlo simulations show that the sensitivity of the CAMEO experiment (in terms of the half-life limit for $ 0\nu 2\beta $ decay) is $\approx 4\times 10^{24}$ yr with a 1 kg source of $^{100}$Mo and $\approx 10^{26}$ yr with $\approx $100 kg of enriched $ ^{116}$CdWO $_4$ crystals placed in the liquid scintillator of the CTF. The last value corresponds to a limit on the neutrino mass of $m_\nu \leq 0.06$ eV. Similarly with 1000 kg of $^{116}$CdWO $_4$ crystals located in the BOREXINO apparatus the neutrino mass limit can be pushed down to $m_\nu \leq 0.02$ eV. [ABSTRACT FROM AUTHOR]