43 research outputs found
A low background facility inside the LVD detector at Gran Sasso
The Large Volume Detector (LVD) in the Gran Sasso Laboratory of INFN is an
observatory mainly devoted to search for neutrinos from core collapse
supernovae. It consists of 1000 tons of liquid scintillator divided in 840
stainless steel tanks 1.5m each. In this letter we present the possibility
for LVD to work both as a passive shield and moderator for the low energy gamma
and neutron background and as an active veto for muons and higher energy
neutrons. An inner region inside the LVD structure ("LVD Core Facility") can be
identified, with a volume of about 30m, with the neutron background typical
of an underground laboratory placed at a much deeper site. This region can be
realized with a negligible impact on the LVD operation and sensitive mass. The
LVD Core Facility could be effectively exploited by a compact experiment for
the search of rare events, such as double beta decay or dark matter.Comment: 5 pages, 2 figure
The Gran Sasso muon puzzle
We carry out a time-series analysis of the combined data from three
experiments measuring the cosmic muon flux at the Gran Sasso laboratory, at a
depth of 3800 m.w.e. These data, taken by the MACRO, LVD and Borexino
experiments, span a period of over 20 years, and correspond to muons with a
threshold energy, at sea level, of around 1.3 TeV. We compare the best-fit
period and phase of the full muon data set with the combined DAMA/NaI and
DAMA/LIBRA data, which spans the same time period, as a test of the hypothesis
that the cosmic ray muon flux is responsible for the annual modulation detected
by DAMA. We find in the muon data a large-amplitude fluctuation with a period
of around one year, and a phase that is incompatible with that of the DAMA
modulation at 5.2 sigmas. Aside from this annual variation, the muon data also
contains a further significant modulation with a period between 10 and 11 years
and a power well above the 99.9% C.L threshold for noise, whose phase
corresponds well with the solar cycle: a surprising observation for such high
energy muons. We see no corresponding long-period oscillation in the
stratospheric temperature data.Comment: Minor changes and clarifications, matches version accepted at JCAP. 5
pages, 3 figure
Supernova Neutrino Spectrum with Matter and Spin Flavor Precession Effects
We consider Majorana neutrino conversions inside supernovae by taking into
account both flavor mixing and the neutrino magnetic moment. We study the
adiabaticity of various possible transitions between the neutrino states for
both normal and inverted hierarchy within the various solar neutrino problem
solutions. From the final mass spectrum within diffrent scenarios, we infer the
consequences of the various conversion effects on the neutronization peak, the
nature of final spectra, and the possible Earth matter effect on the final
fluxes. This enable us to check the sensibility of the SN neutrino flux on
magnetic moment interaction, and narrow down possible scenarios which depend
on: the mass spectrum normal or inverted, the solution of the solar neutrino
problem; and the value of MuxB.Comment: 24pages, 7 figure
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Binary Black Hole Mergers in the first Advanced LIGO Observing Run
The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper we present full results from a search for binary black hole merger signals with total masses up to and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance, which has a 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations we infer stellar-mass binary black hole merger rates lying in the range . These observations are beginning to inform astrophysical predictions of binary black hole formation rates, and indicate that future observing runs of the Advanced detector network will yield many more gravitational wave detections