A 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.
Abstract
Borexino is a large liquid scintillator experiment located at the underground INFN Laboratori Nazionali del Gran Sasso, in Italy. It was designed and built with the primary goal of real-time ...detection of low energy solar neutrinos, and in more than ten years of data taking it has measured all the neutrino fluxes produced in the proton-proton chain, i.e. the main fusion process accounting for 99% of the energy production in the Sun. Recently, after improvements and developments in both hardware and software, Borexino has provided the first observation of solar neutrinos emitted from the subdominant Carbon-Nitrogen-Oxygen (CNO) fusion cycle. All the crucial steps of the analysis strategy adopted to disentangle the signal of CNO neutrinos from backgrounds present in the detector will be described in this article.
Abstract
Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy. The main goal of Borexino is to measure solar neutrinos via elastic ...scattering off electrons in the liquid scintillator. The electrons are then detected by the photo-multiplier tubes via isotropically emitted scintillation photons. However, in the first few nanoseconds after a neutrino interaction, Cherenkov photons (<1% of all detected photons) are also produced in the scintillator for electrons with kinetic energy >0.16 MeV. Borexino has successfully obtained the first directional measurement of sub-MeV solar neutrinos, and the
7
Be solar neutrino interaction rate, through the exploitation of this Cherenkov light signal. This is performed through the so-called
Correlated and Integrated Directionality
(CID) method, by correlating the first few detected photons to the well-known position of the Sun and integrating the angle for a large number of events. This measurement requires a calibration of the relative time differences between Cherenkov and scintillation photons. In Borexino, we obtain this through gamma calibration sources namely,
40
K and
54
Mn. A group velocity correction estimated through the gamma sources is then used for the solar neutrino analysis. This article will discuss the analysis strategy and methods used for this calibration, and provide motivation for a dedicated Cherenkov calibration in next-generation liquid scintillator detectors.
Abstract
Borexino, located at the Laboratori Nazionali del Gran Sasso in Italy, is a liquid scintillator detector that measures solar neutrinos via elastic scattering off electrons. The scintillation ...process of detection makes it impossible to distinguish electrons scattered by neutrinos from the electrons emitted from the decays of radioactive backgrounds. Due to the unprecedented radio-purity achieved by the Borexino detector, the real time spectroscopic detection of solar neutrinos from both the pp chain and CNO fusion cycle of the Sun has been performed. With the newly presented analysis, it is now possible for the first time, to perform the directional detection of the sub-MeV solar neutrinos and extract the
7
Be interaction rate using the few Cherenkov photons emitted at early times, in the direction of scattered electrons with an energy threshold of 0.16 MeV in the liquid scintillator. The angle which correlates the direction of the Sun and the direction of the emitted Cherenkov photons is a key parameter to extract the neutrino signal from data. This article will describe the strategy used in the evaluation of various systematic effects including the geometric conditions of the detector and the data selection cuts that can influence the shape of the directional angle distribution for backgrounds, which is crucial to disentangle the directional sub-MeV solar neutrino signal from the isotropic background in data.
Abstract
The Borexino detector, located at the Laboratori Nazionali del Gran Sasso in Italy, is a radiopure 280 ton liquid scintillator detector with a primary goal to measure low-energy solar ...neutrinos created in the core of the Sun. These neutrinos are a consequence of nuclear fusion reactions in the solar core where Hydrogen is burned into Helium and provide a direct probe of the energy production processes, namely the proton-proton (
pp
) chain and the Carbon-Nitrogen-Oxygen (CNO) cycle. The fusion of Hydrogen in the case of the CNO cycle, which is expected to contribute in the order of less than 1% to the total solar energy, is catalyzed by Carbon, Nitrogen, and Oxygen directly depending on the abundances of these elements in the solar core. The measurement of CNO neutrinos is challenging due to the high spectral correlation with the decay electrons of the background isotope
210
Bi and the pep solar neutrino signal. The experimental achievement of thermal stabilization of the Borexino detector after mid 2016, has opened the possibility to develop a method to constrain the
210
Bi rate through its decay daughter and α emitter
210
Po which can be identified in Borexino with an efficiency close to 100 percent on an event-by-event basis. Moreover, the flux of pep neutrinos can be constrained precisely through a global analysis of solar neutrino data which is independent of the dataset used for the CNO analysis. This conference contribution is dedicated to the first experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun which is at the same time the dominant energy production mechanism in heavier stars compared to the Sun.
Abstract
Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The ...unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at 3800 m w.e. depth have resulted in very low background levels, making Borexino an excellent apparatus for geoneutrino measurements. This article will summarize the recent geoneutrino analysis and results with Borexino, from the period December 2007 to April 2019. The updated statistics and the optimized analysis techniques such as an increased fiducial volume and sophisticated cosmogenic vetoes, have led to more than a two-fold increase in exposure when compared to the previous measurement in 2015, resulting in a significant improvement in the precision. In addition, Borexino has also been able to reject the null hypothesis of the mantle geoneutrino signal with 99% C.L., for the first time, by exploiting the extensive knowledge of the crust surrounding the detector. This article will also include other geological interpretations of the obtained results such as the calculation of the radiogenic heat and the comparison of the results to various predictions. Additionally, upper limits for a hypothetical georeactor that might be present at different locations inside the Earth will also be discussed.
Solar and geoneutrinos Ludhova, L; Agostini, M; Altenmüller, K ...
Journal of physics. Conference series,
12/2021, Letnik:
2156, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Thanks to the progress of neutrino physics, today we are able of exploiting neutrinos as a tool to study astrophysical objects. The latter in turn serve as unique sources of elusive ...neutrinos, which fundamental properties are still to be understood. This contribution attempts to summarize the latest results obtained by measuring neutrinos emitted from the Sun and geoneutrinos produced in radioactive decays inside the Earth, with a particular focus on a recent discovery of the CNO-cycle solar neutrinos by Borexino. Comprehensive measurement of the
pp
-chain solar neutrinos and the first directional detection of sub-MeV solar neutrinos by Borexino, the updated
8
B solar neutrino results of Super-Kamiokande, as well as the latest Borexino and KamLAND geoneutrino measurements are also discussed.
Abstract
Borexino is a 280t liquid scintillator detector at the Laboratori Nazionali del Gran Sasso (LNGS), Italy. Its main goal is the precision spectroscopy of solar neutrinos down to energies of ...0.19 MeV and for this task it features an unprecedented radio-purity and a high scintillation light yield. The solar neutrinos are measured by the elastic scattering off electrons which induce isotropically emitted scintillation photons as well as a sub-dominant number of Cherenkov photons that are detected by photomulitplier tubes. Here we present the first detection of sub-MeV solar neutrinos using their associated Cherenkov photons in a high light yield liquid scintillator detector. In Borexino electrons with E>0.16MeV produce Cherenkov photons, where the ratio of Cherenkov photons from the neutrino scattered electrons is estimated to be < 1% for all PMT hits, so a typical event by event direction reconstruction is not possible. Instead this analysis looks at the integrated signal of the PMT hits of all detected events by correlating the position of each hit PMT relative to the reconstructed position of the event and the well known position of the Sun. In this way it is possible to measure an angular distribution that shows the statistical contribution of Cherenkov photons from the solar neutrino recoil electrons. Using the Geant4-based Borexino Monte Carlo to produce the expected angular distribution for solar neutrinos and background we have measured
8643
−
2058
+2252
neutrino events out of 19904 total events for an energy region around the
7
Be edge between 0.53 MeV and 0.74 MeV.
Borexino has been a neutrino detector based on ultrapure liquid scintillator, located at the Laboratori Nazionali del Gran Sasso, Italy. Its main scientific goal was the real-time measurement of ...solar neutrino fluxes, which play an irreplaceable role for the comprehension of the mechanisms powering our star. Over the past two years, the Borexino collaboration has pursued the improvement of the CNO flux measurement, obtaining further indications about the solar metallicity. In a parallel way, Borexino has demonstrated for the first time the possibility of exploiting the directional Cherenkov information, in a liquid scintillator detector, for the detection of sub-MeV solar neutrinos.
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