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.
Large-scale spatial segregation was assessed by means of radio-telemetry in 48 fallow deer studied for 4 years. Three hypotheses have traditionally been used to explain sexual segregation: (1) the ...predation risk hypothesis, (2) the forage selection hypothesis, (3) the activity budget hypothesis. The first of these seems to be a valid explanation of large-scale segregation in fallow deer at San Rossore, where the use by the two sexes of areas characterized by intense anthropic disturbance, during the day, was compared with other areas not affected by human pressure. Males showed a high use of disturbed areas, both during the day and the night, with the exception of the rutting period, when they reached more remote areas to mate. Females frequented disturbed areas only during the night, with the exception of the birth period, when sexual segregation peaked because females never used these areas, not even during the night. The forage selection hypothesis was invalid on a large scale, considering that no differences between the degree of day and night sexual segregation were to be expected. However, the predation risk hypothesis seems not to be a valid explanation of small-scale sexual segregation, when further subdivisions of disturbed areas are considered, because sexes proved to be segregated also during the night in the area they both used. This emphasizes both the importance of scale in understanding ecological processes, since a combination of many different factors may be responsible for the evolution of sexual segregation in ungulates, and the importance of human pressure in influencing deer behaviour.
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.
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.
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.
The Borexino experiment, located in the Laboratori Nazionali del Gran Sasso in Italy and widely known for its rich Solar Neutrino physics program, has recently celebrated the 10 years of data taking. ...Among the achievements of the Borexino experiment solar program are: a precision measurement of 7Be neutrino flux with uncertainty of 3%, limit on its day/night asymmetry, first spectral measurement of pp-neutrinos, first evidence of monoenergetic pep neutrinos at 5 sigma, 8B neutrinos detection with the lowest visible energy threshold of 3 MeV, observation of season modulation of the 7Be solar neutrino rate at 3.8 sigma and the best current limit on CNO neutrino flux. Borexino is now in its high-purity Phase II data taking, thanks to intense purification campaigns of scintillator in 2010-11 that were very successful in further reducing the already low backgrounds. The advanced tecniques of data analysis were improved, allowing to maximize the signal/noise ratio. The detector was thermally insulated in order to improve the fluid stability. As an outcome, quality of the data has significantly increased leading to new levels of sensitivity to all solar neutrino fluxes. This allows a more sensitive probe for CNO neutrinos relevant to the solar metallicity problem.
PDF
