18 research outputs found
Direct measurement of neutrons induced in lead by cosmic muons at a shallow underground site
Neutron production in lead by cosmic muons has been studied with a Gadolinium
doped liquid scintillator detector. The detector was installed next to the
Muon-Induced Neutron Indirect Detection EXperiment (MINIDEX), permanently
located in the T\"ubingen shallow underground laboratory where the mean muon
energy is approximately 7 GeV. The MINIDEX plastic scintillators were used to
tag muons; the neutrons were detected through neutron capture and
neutron-induced nuclear recoil signals in the liquid scintillator detector.
Results on the rates of observed neutron captures and nuclear recoils are
presented and compared to predictions from GEANT4-9.6 and GEANT4-10.3. The
predicted rates are significantly too low for both versions of GEANT4. For
neutron capture events, the observation exceeds the predictions by factors of and for GEANT4-9.6
and GEANT4-10.3, respectively. For neutron nuclear recoil events, which require
neutron energies above approximately 5 MeV, the factors are even larger, and , respectively.
Also presented is the first statistically significant measurement of the
spectrum of neutrons induced by cosmic muons in lead between 5 and 40 MeV. It
was obtained by unfolding the nuclear recoil spectrum. The observed neutron
spectrum is harder than predicted by GEANT4. An investigation of the
distribution of the time difference between muon tags and nuclear recoil
signals confirms the validity of the unfolding procedure and shows that GEANT4
cannot properly describe the time distribution of nuclear recoil events. In
general, the description of the data is worse for GEANT4-10.3 than for
GEANT4-9.6.Comment: 29 pages, 22 figures, 4 table
Modeling of GERDA Phase II data
The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground
laboratory (LNGS) of INFN is searching for neutrinoless double-beta
() decay of Ge. The technological challenge of GERDA is
to operate in a "background-free" regime in the region of interest (ROI) after
analysis cuts for the full 100kgyr target exposure of the
experiment. A careful modeling and decomposition of the full-range energy
spectrum is essential to predict the shape and composition of events in the ROI
around for the search, to extract a precise
measurement of the half-life of the double-beta decay mode with neutrinos
() and in order to identify the location of residual
impurities. The latter will permit future experiments to build strategies in
order to further lower the background and achieve even better sensitivities. In
this article the background decomposition prior to analysis cuts is presented
for GERDA Phase II. The background model fit yields a flat spectrum in the ROI
with a background index (BI) of cts/(kgkeVyr) for the enriched BEGe data set and
cts/(kgkeVyr) for the
enriched coaxial data set. These values are similar to the one of Gerda Phase I
despite a much larger number of detectors and hence radioactive hardware
components
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Modeling of GERDA Phase II data
The GERmanium Detector Array (Gerda) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double-beta (0νββ) decay of 76Ge. The technological challenge of Gerda is to operate in a “background-free” regime in the region of interest (ROI) after analysis cuts for the full 100 kg·yr target exposure of the experiment. A careful modeling and decomposition of the full-range energy spectrum is essential to predict the shape and composition of events in the ROI around Qββ for the 0νββ search, to extract a precise measurement of the half-life of the double-beta decay mode with neutrinos (2νββ) and in order to identify the location of residual impurities. The latter will permit future experiments to build strategies in order to further lower the background and achieve even better sensitivities. In this article the background decomposition prior to analysis cuts is presented for Gerda Phase II. The background model fit yields a flat spectrum in the ROI with a background index (BI) of 16.04+0.78−0.85⋅10−3 cts/(keV·kg·yr) for the enriched BEGe data set and 14.68+0.47−0.52⋅10−3 cts/(keV·kg·yr) for the enriched coaxial data set. These values are similar to the one of Phase I despite a much larger number of detectors and hence radioactive hardware components
The GERDA Neutrinoless-Double-Beta decay experiment
Neutrinoless double beta (0)-decay is a key
process to gain understanding of the nature of neutrinos.
The GErmanium Detector Array (GERDA) is designed to
search for 0-decay of the isotope Ge.
Germanium crystals enriched in Ge, acting as source and
detector simultaneously, will be submerged directly into an
ultra pure cooling medium that also serves as a radiation
shield. This concept will allow for a reduction of the background
by up to two orders of magnitudes with respect to earlier experiments.
The experiment is currently being installed in hall A of the
underground laboratory of the LNGS, INFN in Italy. Data taking is expected
to start in 2009
MADMAX: A new Dark Matter Axion Search using a dielectric Haloscope
Axions are an intriguing dark matter candidate, emerging from the Peccei-Quinn solution to the strong CP problem. Current experimental searches for axion dark matter focus on axion masses below 40eV. However, if the Peccei-Quinn symmetry is restored after inflation the axion mass is predicted to be in the 100\,eV range. A new project based on axion-photon conversion at the transition between different dielectric media is presented. The axion-photon conversion could be enhanced by a factor over a single mirror by using layers of dielectrics. Within a 10 T magnetic field this could be enough to detect \,eV axions with HEMT linear amplifiers. The proposed design for an experiment is discussed. Results from noise, transmissivity and reflectivity measurements in a prototype setup are presented. The expected sensitivity is shown
MADMAX: A new Dark Matter Axion Search using a dielectric Haloscope
Axions are an intriguing dark matter candidate, emerging from the Peccei-Quinn solution to the strong CP problem. Current experimental searches for axion dark matter focus on axion masses below 40eV. However, if the Peccei-Quinn symmetry is restored after inflation the axion mass is predicted to be in the 100\,eV range. A new project based on axion-photon conversion at the transition between different dielectric media is presented. The axion-photon conversion could be enhanced by a factor over a single mirror by using layers of dielectrics. Within a 10 T magnetic field this could be enough to detect \,eV axions with HEMT linear amplifiers. The proposed design for an experiment is discussed. Results from noise, transmissivity and reflectivity measurements in a prototype setup are presented. The expected sensitivity is shown
MADMAX: A new road to axion dark matter detection
The axion is a hypothetical low-mass boson predicted by the Peccei-Quinn mechanism solving the strong CP problem. It is naturally also a cold dark matter candidate if its mass is below ∼1 meV, thus simultaneously solving two major problems of nature. All existing experimental efforts to detect QCD axions focus on a range of axion masses below ∼25 μeV. The mass range above ∼40 μeV, predicted by modern models in which the Peccei-Quinn symmetry was restored after inflation, could not be explored so far. The MADMAX project is designed to be sensitive for axions with masses (40–400) μeV. The experimental design is based on the idea of enhanced axion-photon conversion in a system with several layers with alternating dielectric constants. The concept and the proposed design of the MADMAX experiment are discussed. Measurements taken with a prototype test setup are discussed. The prospects for reaching sensitivity enough to cover the parameter space predicted for QCD dark matter axions with mass in the range around 100 μeV is presented