Borexino’s search for low-energy neutrino and antineutrino signals correlated with gamma-ray bursts

Abstract

International audienceA search for neutrino and antineutrino events correlated with 2350 gamma-ray bursts (GRBs) is performed with Borexino data collected between December 2007 and November 2015. No statistically significant excess over background is observed. We look for electron antineutrinos ( ν¯e ) that inverse beta decay on protons with energies from 1.8 MeV to 15 MeV and set the best limit on the neutrino fluence from GRBs below 8 MeV. The signals from neutrinos and antineutrinos from GRBs that scatter on electrons are also searched for, a detection channel made possible by the particularly radio-pure scintillator of Borexino. We obtain currently the best limits on the neutrino fluence of all flavors and species below 7 MeV. Finally, time correlations between GRBs and bursts of events are investigated. Our analysis combines two semi-independent data acquisition systems for the first time: the primary Borexino readout optimized for solar neutrino physics up to a few MeV, and a fast waveform digitizer system tuned for events above 1 MeV

Improved measurement of B8 solar neutrinos with 1.5 kt·

“…For this analysis we used the data acquired by both the primary and the FADC DAQ systems, the latter optimized for the acquisition of high energy events [11], following the approach applied in [34]. Collected data correspond to 4.766 live years starting in November 2009, when the FADC system was commissioned, until October 2017.…”

Solar neutrino physics with Borexino

“…A likelihood was built using such a pulse shape parameter, the radial distribution of events, and the simultaneous fit of 11 C-rich and 11 C-subtracted energy spectra. This procedure for determining neutrino fluxes is illustrated in Fig.4, and allowed us to simultaneously fit the Borexino data between ∼200 keV and ∼2.5 MeV, including the interaction rate of pp, 7 Be, pep, and CNO solar neutrinos and the overlapping backgrounds (previous measurements were carried out focusing on narrower energy regions). Figure 4: Illustration of the Phase II Borexino fitting strategy used to simultaneously determine the interaction rate of pp, 7 Be, and pep solar neutrinos.…”

“…The 7 Be and pp neutrino fluxes can be used to compare the relative weight of the two 25.6 which is predicted to be (0.180 ± 0.11) and (0.161 ± 0.10) for HZ and LZ SSM, respectively. This ratio measured by Borexino is R BX = 0.178 +0.027 −0.023 .…”

Search for Low-Energy Signals from Fast Radio Bursts with the Borexino Detector

“…The Borexino experiment ruled out any significant day-night asymmetry of the 7 Be neutrino interaction rate [43] and set new limits on the effective magnetic moment of solar neutrinos [30,44], possible violation of the Pauli exclusion principle [45], on the flux of highenergy solar axions [46], the flux of νe from the Sun and different unknown sources [47,25], heavy sterile neutrino mixing in the 8 B β + -decay [48], the stability of the decay of an electron into a neutrino and a photon [49], non-standard neutrino interactions [50], neutrino and antineutrino fluences in temporal correlation with γray bursts [23], and gravitational wave events [24], and some other rare processes.…”

“…Borexino, a real-time liquid scintillator detector designed for solar neutrino spectroscopy, is located at the Gran Sasso National Laboratory, in Italy [18,19,20,21]. Due to its extremely low background level, large target mass, and low energy threshold, the Borexino detector has been successfully used for studying lowenergy neutrino fluxes from such transients as γ-ray bursts (GRBs), gravitational wave (GW) events and solar flares [22,23,24,25].…”