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 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 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 is a 300 ton sub-MeV liquid scintillator solar neutrino detector which has been running at the Laboratori Nazionali del Gran Sasso (Italy) since 2007. Thanks to its unprecedented ...radio-purity, it was able to measure the flux of 7Be, 8B, pp, and pep solar neutrinos and to detect geo-neutrinos. A reliable simulation of the detector is an invaluable tool for all Borexino physics analyses. The simulation accounts for the energy loss of particles in all the detector components, the generation of the scintillation photons, their propagation within the liquid scintillator volume, and a detailed simulation of the electronics chain. A novel efficient method for simulating the external background which survives the Borexino passive shield was developed. This technique allows to reliably predict the effect of the contamination in the peripheral construction materials. The techniques developed to simulate the Borexino detector and their level of refinement are of possible interest to the neutrino and dark matter communities, especially for current and future large-volume liquid scintillator experiments.
Abstract
The Borexino liquid scintillator neutrino observatory has a unique capability to perform high-precision solar neutrino observations thanks to its exceptional radiopurity and good energy ...resolution (5% at 1 MeV). A comprehensive study of the pp-chain neutrinos was presented that includes the direct measurements of
7
Be, pp and pep neutrino fluxes with the highest precision ever achieved (down to 2.8% in the
7
Be component), the
8
B with the lowest energy threshold, the best limit on CNO neutrinos and the first Borexino limit on hep neutrinos. These results are important to validate the MSW-LMA oscillation paradigm across the full solar energy range and to exclude possible Non-Standard neutrino Interactions (NSIs). In particular the effects of neutrino-flavor-diagonal Neutral-Current (NC) interactions that modify the
v
e
e
and
v
τ
e
couplings while preserving their chiral and flavor structures, have been investigated. At detection, the shape of the electron-recoil spectrum is affected by changes in the
v
e
e
and
v
τ
e
couplings, quantified by the parameters
ε
e
L
/
R
and
ε
τ
L
/
R
. New bounds to all four parameters were obtained, quite stringent compared to the global ones. In particular, the best constraint to-date on
ε
e
L
was achieved. A comprehensive summary of all the recent results on solar neutrinos from Borexino is reported in the present paper.
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 a 3800 m w.e. depth have resulted in very low background levels and have made Borexino an excellent apparatus for geoneutrino measurements. The analysis techniques of the latest geoneutrino results with Borexino were presented using the data obtained from December 2007 to April 2019, corresponding to an exposure of (1.12 ± 0.05) × 10
32
protons × yr. Enhanced analysis techniques, such as an increased fiducial volume, improved veto for cosmogenic backgrounds, extended energy and coincidence time windows, as well as a more efficient
α/β
particle discrimination have been adopted in this measurement. The updated statistics and these elaborate resulted in a geoneutrino signal of
47.0
−
7.7
+
8.4
(
stat
)
−
1.9
+
2.4
(
sys
)
TNU
with
−
17.2
+
18.3
%
total precision.
Ten years of cosmic muons observation with Borexino D’Angelo, Davide; Agostini, M.; Altenmüller, K. ...
Journal of physics. Conference series,
01/2020, Letnik:
1468, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Abstract
The Borexino detector at Gran Sasso has now accumulated over ten years of continuous data which represent a magnificent opportunity to study the cosmic muon flux at a deep underground ...location. We present here a precision measurement of the flux and of the expected seasonal modulation. We present the correlation with the atmospheric temperature variations from global atmospheric models. We measure the correlation parameters and infer the kaon-to-pion ratio in the production of cosmic muons from high energy primaries. We also find evidence of a long term modulation that is not present in the atmospheric data and we investigate a possible positive correlation with the solar activity. Finally we observe a seasonal modulation of the production rate of cosmogenic neutrons that is in phase with the muon modulation but shows a surprisingly larger amplitude.
Borexino is a 300 ton sub-MeV liquid scintillator solar neutrino detector which has been running at the Laboratori Nazionali del Gran Sasso (Italy) since 2007. Thanks to its unprecedented ...radio-purity, it was able to measure the flux of 7Be, 8B, pp, and pep solar neutrinos and to detect geo-neutrinos. A reliable simulation of the detector is an invaluable tool for all Borexino physics analyses. The simulation accounts for the energy loss of particles in all the detector components, the generation of the scintillation photons, their propagation within the liquid scintillator volume, and a detailed simulation of the electronics chain. A novel efficient method for simulating the external background which survives the Borexino passive shield was developed. This technique allows to reliably predict the effect of the contamination in the peripheral construction materials. The techniques developed to simulate the Borexino detector and their level of refinement are of possible interest to the neutrino and dark matter communities, especially for current and future large-volume liquid scintillator experiments.
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