298 research outputs found
Commissioning the Auger Prime Radio Detector. Paving the Way for Mass Separation
No full textContains fulltext :
309692.pdf (Publisher’s version ) (Open Access)High-energy cosmic rays provide a unique window into the universe's most energetic astrophysical processes. The Pierre Auger Observatory, dedicated to studying these cosmic rays, is undergoing an upgrade called AugerPrime, aimed at enhancing its sensitivity to the primary particle types. The thesis focuses on the commissioning and performance assessment of the AugerPrime Radio Detector. Firstly, it details the background noise monitoring and the performance evaluation, both essential for accurate air shower reconstructions. Next, the thesis proceeds with a comprehensive pilot calibration of the Radio Detector using radio sky emissions while describing the calibration method in depth and exploring the effects of various factors on the calibration parameters.
The work further examines systematic uncertainties arising from mismatches between theoretical antenna models and the actual station setups, quantifying their impact on the reconstructed electromagnetic energy and energy fluence.
The thesis concludes with an analysis of the initial data. It revealed a good correlation between measured and expected number of radio event rates and satisfying agreement between measured quantities at the channel and station levels and their corresponding values from reconstructed simulations. Moreover, an investigation of the muon content in relation with the radiation energy demonstrated a promising agreement with reference data from previous studies.Radboud University, 16 september 2024Promotor : Hörandel, J.R.212 p
CD1b-mycolic acid tetramers demonstrate T-cell fine specificity for mycobacterial lipid tails
No full textMycobacterium tuberculosis synthesizes a thick cell wall comprised of mycolic acids (MA), which are foreign antigens for human T cells. T-cell clones from multiple donors were used to determine the fine specificity of MA recognition by human αβ T cells. Most CD1-presented lipid antigens contain large hydrophilic head groups comprised of carbohydrates or peptides that dominate patterns of T-cell specificity. MA diverges from the consensus antigen motif in that it lacks a head group. Using multiple forms of natural and synthetic MA and MA-specific T-cells with different T-cell receptors, we found that, unlike antigens with larger head groups, lipid length strongly controlled T-cell responses to MA. In addition, the three forms of MA that naturally occur in M. tuberculosis that differ in modifications on the lipid tail, differ in their potency for activating MA-specific T-cell clones. Thus, naturally occurring MA forms should be considered as separate, partly cross-reactive antigens. Two of the three forms of MA could be loaded onto human CD1b proteins, creating working CD1b-MA tetramers. The creation of CD1b-MA tetramers represents a new tool for future studies that track the effector functions and kinetics of MA-specific T-cells ex vivo
Uncertainties of the 30-408 MHz Galactic emission as a calibration source for radio detectors in astroparticle physics
No full textContext. Arrays of radio antennas have proven to be successful in
astroparticle physics with the observation of extensive air showers initiated
by high-energy cosmic rays in the Earth's atmosphere. Accurate determination of
the energy scale of the primary particles' energies requires an absolute
calibration of the radio antennas for which, in recent years, the utilization
of the Galactic emission as a reference source has emerged as a potential
standard. Aims. To apply the "Galactic Calibration", a proper estimation of the
systematic uncertainties on the prediction of the Galactic emission from sky
models is necessary, which we aim to determine on a global level as well as for
the specific cases of selected radio arrays. We further aim to quantify the
influence of the quiet Sun on the Galactic Calibration. Methods. We look at
four different sky models that predict the full-sky Galactic emission in the
frequency range from 30 to 408 MHz and compare them. We make an inventory of
the reference maps on which they rely and use the output of the models to
determine their global level of agreement. Next, we take the sky exposures and
frequency bands of selected radio arrays into account and repeat the comparison
for each of them. Finally, we study the relative influence of the Sun in its
quiet state by projecting it onto the sky with brightness data from recent
measurements. Results. We find systematic uncertainty of 12% on the predicted
power from the Galactic emission, which scales to approximately half of that
value as the uncertainty on the determination of the energy of cosmic
particles. When looking at the selected radio arrays, the uncertainty on the
predicted power varies between 10% and 19%. The influence of the quiet Sun
turns out to be insignificant at the lowest frequencies but increases to a
relative contribution of ~ 20% around 400 MHz.Comment: 16 pages, 7 figure
Uncertainties of the 30–408 MHz Galactic emission as a calibration source for radio detectors in astroparticle physics
No full textContext. Arrays of radio antennas have proven to be successful in astroparticle physics with the observation of extensive air showers initiated by high-energy cosmic rays in the Earth’s atmosphere. Accurate determination of the energy scale of the primary particles’ energies requires an absolute calibration of the radio antennas for which, in recent years, the utilization of the Galactic emission as a reference source has emerged as a potential standard.
Aims. To apply the “Galactic calibration” a proper estimation of the systematic uncertainties on the prediction of the Galactic emission from sky models is necessary, which we aim to quantify on a global level and for the specific cases of selected radio arrays. We further aim to determine the influence of additional natural radio sources on the Galactic calibration.
Methods. We compared seven different sky models that predict the full-sky Galactic emission in the frequency range from 30 to 408 MHz. We made an inventory of the reference maps on which they rely and used the output of the models to determine their global level of agreement. We subsequently took typical sky exposures and the frequency bands of selected radio arrays into account and repeated the comparison for each of them. Finally, we studied and discuss the relative influence of the quiet Sun, the ionosphere, and Jupiter.
Results. We find a systematic uncertainty of 14.3% on the predicted power from the Galactic emission, which scales to approximately half of that value as the uncertainty on the determination of the energy of cosmic particles. When looking at the selected radio arrays, the uncertainty on the predicted power varies between 11.7% and 21.5%. The influence of the quiet Sun turns out to be insignificant at the lowest frequencies but increases to a relative contribution of ~30% around 400 MHz
Total Synthesis of a Mycolic Acid from Mycobacterium tuberculosis
No full textIn Mycobacterium tuberculosis, mycolic acids and their glycerol, glucose, and trehalose esters ("cord factor") form the main part of the mycomembrane. Despite their first isolation almost a century ago, full stereochemical evaluation is lacking, as is a scalable synthesis required for accurate immunological, including vaccination, studies. Herein, we report an efficient, convergent, gram-scale synthesis of four stereo-isomers of a mycolic acid and its glucose ester. Binding to the antigen presenting protein CD1b and T cell activation studies are used to confirm the antigenicity of the synthetic material. The absolute stereochemistry of the syn-methoxy methyl moiety in natural material is evaluated by comparing its optical rotation with that of synthetic material.</p
First results from the AugerPrime Radio Detector
No full textThe Pierre Auger Observatory investigates the properties of the highest-energy cosmic rays with unprecedented precision. The aim of the AugerPrime upgrade is to improve the sensitivity to the primary particle type. The improved mass sensitivity is the key to exploring the origin of the highest-energy particles in the Universe. The purpose of the Radio Detector (as part of AugerPrime) is to extend the sensitivity of the mass measurements to zenith angles in the range from 65° to 85°. A radio antenna, sensitive in two polarization directions and covering a bandwidth from 30 to 80 MHz, will be added to each of the 1661 surface detector stations over the full 3000 km^2 area, forming the world’s largest radio array for the detection of cosmic particles. Since November 2019, an engineering array comprised of ten stations has been installed in the field. The radio antennas are calibrated using the Galactic (diffuse) emission. The sidereal
modulation of this signal is monitored continuously and is used to obtain an end-to-end calibration from the receiving antenna to the ADC in the read-out electronics. The calibration method and first results will be presented. The engineering array is also fully integrated in the data acquisition of the Observatory and records air showers regularly. The first air showers detected simultaneously with the water-Cherenkov detectors and the Radio Detectors will be presented. Simulations of the detected showers, based on the reconstructed quantities, have been conducted with CORSIKA/CoREAS. A comparison of the measured radio signals with those predicted by simulations exhibits satisfying agreement
Combined Search for UHE Neutrinos from Binary Black Hole Mergers with the Pierre Auger Observatory
No full textWe present searches for ultra-high energy (UHE) neutrinos (> 0.1 EeV) with the Pierre Auger Observatory, following up binary black hole (BBH) mergers detected by the LIGO and Virgo detectors via gravitational waves (GWs). In this work, the so-far published BBH mergers are combined as standard candles with a hypothetical isotropic UHE neutrino luminosity L(t − t0) as a function of the time after the respective merger, t − t0. The UHE neutrino emission spectrum is assumed to follow a power law distribution ∝ Ev−2. Using these assumptions, L(t − t0) is probed, taking into account the instantaneous effective area of the Pierre Auger Observatory to UHE neutrinos and the 3D sky localizations of the sources. No UHE neutrino candidates have been found and upper limits on L(t − t0) are obtained for the hypothetical cases of emissions lasting 24 hours and 60 days after the merger, respectively. The corresponding upper limit on the total energy per source emitted in UHE neutrinos does not depend on the emission duration and demonstrates the competitiveness of the Pierre Auger Observatory with dedicated neutrino telescopes
Combined Search for UHE Neutrinos from Binary Black Hole Mergers with the Pierre Auger Observatory
No full textWe present searches for ultra-high energy (UHE) neutrinos (>0.1EeV) with the Pierre Auger Observatory, following up binary black hole (BBH) mergers detected by the LIGO and Virgo detectors via gravitational waves (GWs). In this work, the so-far published BBH~mergers are combined as standard candles with a hypothetical isotropic UHE~neutrino luminosity L(t−t) as a function of the time after the respective merger, t−t. The UHE~neutrino emission spectrum is assumed to follow a power law distribution ∝E. Using these assumptions, L(t−t) is probed, taking into account the instantaneous effective area of the Pierre Auger Observatory to UHE~neutrinos and the 3D sky localizations of the sources. No UHE~neutrino candidates have been found and upper limits on L(t−t) are obtained for the hypothetical cases of emissions lasting 24 hours and 60 days after the merger, respectively. The corresponding upper limit on the total energy per source emitted in UHE~neutrinos does not depend on the emission duration and demonstrates the competitiveness of the Pierre Auger Observatory with dedicated neutrino telescopes
Reconstruction of Events Recorded with the Water-Cherenkov and Scintillator Surface Detectors of the Pierre Auger Observatory
No full textThe XY Scanner - A Versatile Method of the Absolute End-to-End Calibration of Fluorescence Detectors
No full text- …
