54 research outputs found
An extensive-air-shower-like event registered with the TUS orbital detector
TUS (Tracking Ultraviolet Set-up) is the world's first orbital detector of
ultra-high-energy cosmic rays (UHECRs). It was launched into orbit on 28th
April 2016 as a part of the scientific payload of the Lomonosov satellite. The
main aim of the mission was to test the technique of measuring the ultraviolet
fluorescence and Cherenkov radiation of extensive air showers generated by
primary cosmic rays with energies above ~100 EeV in the Earth atmosphere from
space. During its operation for 1.5 years, TUS registered almost 80,000 events
with a few of them satisfying conditions anticipated for extensive air showers
(EASs) initiated by UHECRs. Here we discuss an event registered on 3rd October
2016. The event was measured in perfect observation conditions as an
ultraviolet track in the nocturnal atmosphere of the Earth, with the kinematics
and the light curve similar to those expected from an EAS. A reconstruction of
parameters of a primary particle gave the zenith angle around 44 but an
extreme energy not compatible with the cosmic ray energy spectrum obtained with
ground-based experiments. We discuss in details all conditions of registering
the event, explain the reconstruction procedure and its limitations and comment
on possible sources of the signal, both of anthropogenic and astrophysical
origin. We believe this detection represents a significant milestone in the
space-based observation of UHECRs because it proves the capability of an
orbital telescope to detect light signals with the apparent motion and light
shape similar to what are expected from EASs. This is important for the
on-going development of the future missions KLYPVE-EUSO and POEMMA, aimed for
studying UHECRs from space.Comment: 24 pages; v2: important changes to address comments by the anonymous
referee; main conclusions unchange
Correlation between Antioxidant Enzymes Activity and Intraerythrocyte Concentration of Fe, Mg, Zn, Cu in Pulmonary Arterial Hypertension and Cor Pulmonale in Children with Congenital Lung Disease and Cystic Fibrosis
Significant changes in the levels of the potential prooxidant Cu (increase) and the antioxidant Zn (decrease) in plasma were revealed in children having bronchopulmonary dysplasia (BPD) complicated by pulmonary arterial hypertension (PAH) and chronic cor pulmonale (CCP) when compared with the control. The Zn / Cu ratio in the blood plasma of patients with BPD, especially in CCP, was found to be lower than in the control group (p<0.001). This could indicate the activation of the prooxidant processes; simultaneously, the total antioxidant status (AOS) decreased. No significant increase in the intracellular free (“ionized” (i)) form of magnesium (iMg) was found; in fact, the concentration of iFe in all the patient groups was higher than in the control. An increase in the iCu and iZn levels (nonprotein-bound) was observed in the blood cells of the affected children. A significant increase in the glutathione peroxidase activity in the CCP patients may indicate an accumulation of organic peroxides, and partially compensate for the lesser activity of superoxide dismutase (SOD) and other antioxidants. The Zn / Cu and iZn/ iCu ratios were reduced in patients with CCP when compared with patients with PD without CCP
Cryogenic characterization of a LiAlO 2 crystal and new results on spin-dependent dark matter interactions with ordinary matter: CRESST Collaboration
In this work, a first cryogenic characterization of a scintillating LiAlO 2 single crystal is presented. The results achieved show that this material holds great potential as a target for direct dark matter search experiments. Three different detector modules obtained from one crystal grown at the Leibniz-Institut für Kristallzüchtung (IKZ) have been tested to study different properties at cryogenic temperatures. Firstly, two 2.8 g twin crystals were used to build different detector modules which were operated in an above-ground laboratory at the Max Planck Institute for Physics (MPP) in Munich, Germany. The first detector module was used to study the scintillation properties of LiAlO 2 at cryogenic temperatures. The second achieved an energy threshold of (213.02 ± 1.48) eV which allows setting a competitive limit on the spin-dependent dark matter particle-proton scattering cross section for dark matter particle masses between 350MeV/c2 and 1.50GeV/c2. Secondly, a detector module with a 373 g LiAlO 2 crystal as the main absorber was tested in an underground facility at the Laboratori Nazionali del Gran Sasso (LNGS): from this measurement it was possible to determine the radiopurity of the crystal and study the feasibility of using this material as a neutron flux monitor for low-background experiments. © 2020, The Author(s)
Observation of a low energy nuclear recoil peak in the neutron calibration data of the CRESST-III Experiment
New-generation direct searches for low mass dark matter feature detection
thresholds at energies well below 100 eV, much lower than the energies of
commonly used X-ray calibration sources. This requires new calibration sources
with sub-keV energies. When searching for nuclear recoil signals, the
calibration source should ideally cause mono-energetic nuclear recoils in the
relevant energy range. Recently, a new calibration method based on the
radiative neutron capture on W with subsequent de-excitation via single
-emission leading to a nuclear recoil peak at 112 eV was proposed. The
CRESST-III dark matter search operated several CaWO-based detector
modules with detection thresholds below 100 eV in the past years. We report the
observation of a peak around the expected energy of 112 eV in the data of three
different detector modules recorded while irradiated with neutrons from
different AmBe calibration sources. We compare the properties of the observed
peaks with Geant-4 simulations and assess the prospects of using this for the
energy calibration of CRESST-III detectors.Comment: 8 pages, 4 figures; submitted to Phys. Rev.
Testing spin-dependent dark matter interactions with lithium aluminate targets in CRESST-III
In the past decades, numerous experiments have emerged to unveil the nature
of dark matter, one of the most discussed open questions in modern particle
physics. Among them, the CRESST experiment, located at the Laboratori Nazionali
del Gran Sasso, operates scintillating crystals as cryogenic phonon detectors.
In this work, we present first results from the operation of two detector
modules which both have 10.46 g LiAlO targets in CRESST-III. The lithium
contents in the crystal are Li, with an odd number of protons and neutrons,
and Li, with an odd number of protons. By considering both isotopes of
lithium and Al, we set the currently strongest cross section upper
limits on spin-dependent interaction of dark matter with protons and neutrons
for the mass region between 0.25 and 1.5 GeV/c.Comment: 9 pages, 8 figure
High-Dimensional Bayesian Likelihood Normalisation for CRESST's Background Model
Using CaWO crystals as cryogenic calorimeters, the CRESST experiment
searches for nuclear recoils caused by the scattering of potential Dark Matter
particles. A reliable identification of a potential signal crucially depends on
an accurate background model. In this work we introduce an improved
normalisation method for CRESST's model of the electromagnetic backgrounds.
Spectral templates, based on Geant4 simulations, are normalised via a Bayesian
likelihood fit to experimental background data. Contrary to our previous work,
no assumption of partial secular equilibrium is required, which results in a
more robust and versatile applicability. Furthermore, considering the
correlation between all background components allows us to explain 82.7% of the
experimental background within [1 keV, 40 keV], an improvement of 18.6%
compared to our previous method.Comment: 24 pages, 14 figures, submitted to EPJ
Latest observations on the low energy excess in CRESST-III
The CRESST experiment observes an unexplained excess of events at low
energies. In the current CRESST-III data-taking campaign we are operating
detector modules with different designs to narrow down the possible
explanations. In this work, we show first observations of the ongoing
measurement, focusing on the comparison of time, energy and temperature
dependence of the excess in several detectors. These exclude dark matter,
radioactive backgrounds and intrinsic sources related to the crystal bulk as a
major contribution.Comment: 10 pages, 5 figures; to be published in IDM2022 proceeding
Development of a compact muon veto for the nucleus experiment
The Nucleus experiment aims to measure coherent elastic neutrino nucleus scattering of reactor anti-neutrinos using cryogenic calorimeters. Operating at an overburden of 3 meters of water equivalent, muon-induced backgrounds are expected to be one of the dominant background contributions. Besides a high efficiency to identify muon events passing the experimental setup, the Nucleus muon veto has to fulfill tight spatial requirements to fit the constraints given by the experimental site and to minimize the induced detector dead-time. We developed highly efficient and compact muon veto modules based on plastic scintillators equipped with wavelength shifting fibers and silicon photo multipliers to collect and detect the scintillation light. In this paper, we present the full characterization of a prototype module with different light read-out configurations. We conclude that an efficient and compact muon veto system can be built for the Nucleus experiment from a cube assembly of the developed modules. Simulations show that an efficiency for muon identification of >99 % and an associated rate of 325 Hz is achievable, matching the requirements of the Nucleus experiment
Detector development for the CRESST experiment
Recently low-mass dark matter direct searches have been hindered by a low
energy background, drastically reducing the physics reach of the experiments.
In the CRESST-III experiment, this signal is characterised by a significant
increase of events below 200 eV. As the origin of this background is still
unknown, it became necessary to develop new detector designs to reach a better
understanding of the observations. Within the CRESST collaboration, three new
different detector layouts have been developed and they are presented in this
contribution.Comment: 8 pages, 4 figure
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