The Borexino detector has convincingly shown its outstanding performance in the in the sub-MeV regime through its unprecedented accomplishments in the solar and geo-neutrinos detection, which make it ...the ideal tool to unambiguously test the long-standing issue of the existence of a sterile neutrino, as suggested by several anomalies: the outputs of the LSND and Miniboone experiments, the results of the source calibration of the two Gallium solar ν experiments, and the recently hinted reactor anomaly. The SOX project will exploit two sources, based on chromium and cerium, which deployed under the experiment will emit two intense beams of (Cr) and (Ce). Interacting in the active volume of the liquid scintillator, each beam would create a spatial wave pattern in case of oscillation of the (or ) into the sterile state, which would be the smoking gun proving the existence of the new sterile member of the neutrino family. Otherwise, its absence will allow setting very stringent limit on its existence.
The decays of super(214)Po into super(210)Pb and of super(212)Po into super(208)Pb tagged by the previous decays from super(214)Bi and super(212)Bi have been studied inserting quartz vials inside the ...Counting Test Facility (CTF) at the underground laboratory in Gran Sasso (LNGS). We find that the mean lifetime of super(214)Po is (236.00 plus or minus 0.42(stat) plus or minus 0.15(syst)) mu s and that of super(212)Po is (425.1 plus or minus 0.9(stat) plus or minus 1.2(syst)) ns. Our results are compatible with previous measurements, have a much better signal to background ratio, and reduce the overall uncertainties.
The Sun is fueled by a series of nuclear reactions that produce the energy that makes it shine. The primary reaction is the fusion of two protons into a deuteron, a positron and a neutrino. These ...neutrinos constitute the vast majority of neutrinos reaching Earth, providing us with key information about what goes on at the core of our star. Several experiments have now confirmed the observation of neutrino oscillations by detecting neutrinos from secondary nuclear processes in the Sun; this is the first direct spectral measurement of the neutrinos from the keystone proton-proton fusion. This observation is a crucial step towards the completion of the spectroscopy of pp-chain neutrinos, as well as further validation of the LMA-MSW model of neutrino oscillations.
The detection and measurement of gravitational-waves from coalescing neutron-star binary systems is an important science goal for groundbased gravitational-wave detectors. In addition to emitting ...gravitational-waves at frequencies that span the most sensitive bands of the LIGO and Virgo detectors, these sources are also amongst the most likely to produce an electromagnetic counterpart to the gravitational-wave emission. A joint detection of the gravitational-wave and electromagnetic signals would provide a powerful new probe for astronomy. During the period between Sep 19 and Oct 20, 2010, the first low-latency search for gravitational-waves from binary inspirals in LIGO and Virgo data was conducted. Over the course of the science run, three gravitational-wave triggers passed all of the low-latency selection cuts. Of these, one was followed up by several of our observational partners. Analysis of the gravitational-wave data leads to an estimated false alarm rate of once every 6.4 days, falling far short of the requirement for a detection based solely on gravitational-wave data.
The decays of (214)Po into (210)Pb and of (212)Po into (208)Pb tagged by the previous decays from (214)Bi and (212)Bi have been studied inserting quartz vials inside the Counting Test Facility (CTF) ...at the underground laboratory in Gran Sasso (LNGS). We find that the mean lifetime of (214)Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of (212)Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results are compatible with previous measurements, have a much better signal to background ratio, and reduce the overall uncertainties.
The decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the previous decays from 214Bi and 212Bi have been studied inserting quartz vials inside the Counting Test Facility (CTF) at the ...underground laboratory in Gran Sasso (LNGS). We find that the mean lifetime of 214Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of 212Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results are compatible with previous measurements, have a much better signal to background ratio, and reduce the overall uncertainties.
We report on the study of a new liquid scintillator target for neutrino interactions in the framework of the research and development program of the Borexino solar neutrino experiment. The ...scintillator consists of 1,2-dimethyl-4-(1-phenylethyl)-benzene (phenyl-o-xylylethane, PXE) as solvent and 1,4-diphenylbenzene (para-Terphenyl, p-Tp) as primary and 1,4-bis(2-methylstyryl)benzene (bis-MSB) as secondary solute. The density close to that of water and the high flash point makes it an attractive option for large scintillation detectors in general. The study focused on optical properties, radioactive trace impurities and novel purification techniques of the scintillator. Attenuation lengths of the scintillator mixture of 12
m at 430
nm were achieved after purification with an alumina column. A radiocarbon isotopic ratio of
C
14
/
C
12
=
9.1
×
10
-
18
has been measured in the scintillator. Initial trace impurities, e.g.
238U
at
3.2
×
10
-
14
g
/
g
could be purified to levels below
1
×
10
-
17
g
/
g
by silica gel solid column purification.
We observed, for the first time, solar neutrinos in the 1.0-1.5 MeV energy range. We determined the rate of pep solar neutrino interactions in Borexino to be 3.1+ or -0.6 sub(stat)+ or -0.3 sub(syst) ...counts/(day times 100 ton). Assuming the pep neutrino flux predicted by the Standard Solar Model, we obtained a constraint on the CNO solar neutrino interaction rate of <7.9 counts/(day times 100 ton) (95% C.L.). The absence of the solar neutrino signal is disfavored at 99.97% C.L., while the absence of the pep signal is disfavored at 98% C.L. The necessary sensitivity was achieved by adopting data analysis techniques for the rejection of cosmogenic super(11)C, the dominant background in the 1-2 MeV region. Assuming the MSW-LMA solution to solar neutrino oscillations, these values correspond to solar neutrino fluxes of (1.6+ or -0.3)x10 super(8) cm super(-2)s super(-1) and <7.7x10 super(8) cm super(-2)s super(-1) (95% C.L.), respectively, in agreement with both the High and Low Metallicity Standard Solar Models. These results represent the first direct evidence of the pep neutrino signal and the strongest constraint of the CNO solar neutrino flux to date.
A very high radiopurity level of its scintillator and detector location far away from the European nuclear reactors makes Borexino a very sensitive tool for antineutrino studies. Spectral ...contributions corresponding to two known antineutrino sources were reported in a recently published paper 1: v sub(e)s produced in European nuclear reactors and geo-neutrinos, produced in beta decays of isotopes along the decay chains of long-lived super(238)U and super(232)Th distributed within the Earth's interior. A sensitive search for other antineutrino sources has been performed.
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