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.
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.
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.
The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In ...this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Y sub(n) = (3.10 + or - 0.11) times 10 super(-4) sub(n)/( mu times (g/cm super(2))). The distance prole between the parent muon track and the neutron capture point has the average value lambda = (81.5 + or - 2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for super(12)N, super(12)B, super(8)He, super(9)C, super(9)Li, super(8)B, super(6)He, super(8)Li, super(11)Be, super(10)C and super(11)C. All results are compared with Monte Carlo simulation predictions using the Fluka and GEANT4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being super(11)C yield for which both codes return about 50% lower values. The predicted mu -n distance prole and the neutron multiplicity distribution are found to be overall consistent with data.
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.
Updated geoneutrino measurement with Borexino Ludhova, Livia; Agostini, M.; Altenmüller, K. ...
Journal of physics. Conference series,
03/2020, Letnik:
1468, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
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 has made Borexino an excellent apparatus for geoneutrino measurements. The new update of the Borexino geoneutrino measurement, using the data obtained from December 2007 to April 2019, has been presented. Enhanced analysis techniques, adopted in this measurement, have been also presented (poster presentation #39 by S. Kumaran). The updated statistics and the new elaborate analysis have led to more than a factor two increase in exposure ((1.12 ± 0.05) × 10
32
protons × yr) when compared to the latest Borexino result from 2015. The resulting geoneutrino signal of
47.0
−
7.7
+
8.4
(
stat
)
−
1.9
+
2.4
(
sys
)
TNU has
−
17.2
+
18.3
%
total precision. The geological interpretations of this measurement have been discussed. In particular, the 99% C.L. observation of the mantle signal by exploiting the relatively well-known lithospheric contribution, the estimation of the radiogenic heat, as well as the comparison of these results to the predictions based on different geological models. The upper limits on the power of a hypothetical georeactor that might be present at different locations inside the Earth have been set.
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.
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.
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