D. Veberic | Searcharxiv

arXiv2026

Origins of Cosmic Rays in the Galactic-extragalactic Transition Energy Range

Cosmic rays arrive at Earth with energies ranging from $10^9$ to over $10^{20}$ eV. One of the open questions in high-energy cosmic ray science concerns the origin of the highest-energy cosmic rays that can be accelerated by Galactic sources, and the transition energy beyond which only extragalactic sources can provide. Measuring the mass composition gives essential information for comparing measurements to source and propagation models, both from the abundances at the source and from the maximum attainable energy which is proportional to the particle charge (and hence its mass). The highest-energy cosmic rays from the Galaxy are found in a range of $10^{16}$ to $10^{18}$ eV which is well suited for radio detection. Building on a decade of experience in measuring cosmic rays at LOFAR, we show that SKA-Low, augmented with an array of small particle detectors, is well suited to advance the field by measuring the mass composition of cosmic rays across this energy range.

astro-ph.HE↗

arXiv2018

An integrated general purpose SiPM based optical module with a high dynamic range

Silicon photomultipliers (SiPMs) are semiconductor-based light-sensors offering a high gain, a mechanically and optically robust design and high photon detection efficiency. Due to these characteristics, they started to replace conventional photomultiplier tubes in many applications in recent years. This paper presents an optical module based on SiPMs designed for the application in scintillators as well as lab measurements. The module hosts the SiPM bias voltage supply and three pre-amplifiers with different gain levels to exploit the full dynamic range of the SiPMs. Two SiPMs, read-out in parallel, are equipped with light guides to increase the sensitive area. The light guides are optimized for the read-out of wavelength shifting fibers as used in many plastic scintillator detectors. The optical and electrical performance of the module is characterized in detail in laboratory measurements. Prototypes have been installed and tested in a modified version of the Scintillator Surface Detector developed for AugerPrime, the upgrade of the Pierre Auger Observatory. The SiPM module is operated in the Argentinian Pampas and first data proves its usability in such harsh environments.

physics.ins-det↗

arXiv2007

The Offline Software Framework of the Pierre Auger Observatory

The Pierre Auger Observatory is designed to unveil the nature and the origins of the highest energy cosmic rays. The large and geographically dispersed collaboration of physicists and the wide-ranging collection of simulation and reconstruction tasks pose some special challenges for the offline analysis software. We have designed and implemented a general purpose framework which allows collaborators to contribute algorithms and sequencing instructions to build up the variety of applications they require. The framework includes machinery to manage these user codes, to organize the abundance of user-contributed configuration files, to facilitate multi-format file handling, and to provide access to event and time-dependent detector information which can reside in various data sources. A number of utilities are also provided, including a novel geometry package which allows manipulation of abstract geometrical objects independent of coordinate system choice. The framework is implemented in C++, and takes advantage of object oriented design and common open source tools, while keeping the user side simple enough for C++ novices to learn in a reasonable time. The distribution system incorporates unit and acceptance testing in order to support rapid development of both the core framework and contributed user code.

astro-ph↗

arXiv2007

The Lidar System of the Pierre Auger Observatory

The Pierre Auger Observatory in Malargue, Argentina, is designed to study the origin of ultrahigh energy cosmic rays with energies above 10^18 eV. The energy calibration of the detector is based on a system of four air fluorescence detectors. To obtain reliable calorimetric information from the fluorescence stations, the atmospheric conditions at the experiment's site need to be monitored continuously during operation. One of the components of the observatory's atmospheric monitoring system is a set of four elastic backscatter lidar stations, one station at each of the fluorescence detector sites. This paper describes the design, current status, standard operation procedure, and performance of the lidar system of the Pierre Auger Observatory.

astro-ph↗

arXiv2006

The Offline Software Framework of the Pierre Auger Observatory

The Pierre Auger Observatory is designed to unveil the nature and the origins of the highest energy cosmic rays. The large and geographically dispersed collaboration of physicists and the wide-ranging collection of simulation and reconstruction tasks pose some special challenges for the offline analysis software. We have designed and implemented a general purpose framework which allows collaborators to contribute algorithms and sequencing instructions to build up the variety of applications they require. The framework includes machinery to manage these user codes, to organize the abundance of user-contributed configuration files, to facilitate multi-format file handling, and to provide access to event and time-dependent detector information which can reside in various data sources. A number of utilities are also provided, including a novel geometry package which allows manipulation of abstract geometrical objects independent of coordinate system choice. The framework is implemented in C++, and takes advantage of object oriented design and common open source tools, while keeping the user side simple enough for C++ novices to learn in a reasonable time. The distribution system incorporates unit and acceptance testing in order to support rapid development of both the core framework and contributed user code.

astro-ph↗

arXiv2003

Pierre Auger Atmosphere-Monitoring Lidar System

The fluorescence-detection techniques of cosmic-ray air-shower experiments require precise knowledge of atmospheric properties to reconstruct air-shower energies. Up to now, the atmosphere in desert-like areas was assumed to be stable enough so that occasional calibration of atmospheric attenuation would suffice to reconstruct shower profiles. However, serious difficulties have been reported in recent fluorescence-detector experiments causing systematic errors in cosmic ray spectra at extreme energies. Therefore, a scanning backscatter lidar system has been constructed for the Pierre Auger Observatory in Malargue, Argentina, where on-line atmospheric monitoring will be performed. One lidar system is already deployed at the Los Leones fluorescence detector site and the second one is currently (April 2003) under construction at the Coihueco site. Next to the established ones, a novel analysis method with assumption on horizontal invariance, using multi-angle measurements is shown to unambiguously measure optical depth, as well as absorption and backscatter coefficient.

astro-ph↗

arXiv2002

Scanning Lidar Based Atmospheric Monitoring for Fluorescent Detectors of Cosmic Showers

Measurements of the cosmic-ray air-shower fluorescence at extreme energies require precise knowledge of atmospheric conditions. The absolute calibration of the cosmic-ray energy depends on the absorption of fluorescence light between its origin and point of its detection. To reconstruct basic atmospheric parameters we review a novel analysis method based on two- and multi-angle measurements performed by the scanning backscatter lidar system. Applied inversion methods, optical depth, absorption and backscatter coefficient, as well as other parameters that enter the lidar equation are discussed in connection to the attenuation of the light traveling from shower to fluorescence detector.

hep-ex↗

arXiv2002

Diamagnetic Properties of Doped Antiferromagnets

Finite-temperature diamagnetic properties of doped antiferromagnets as modeled by the two-dimensional t-J model were investigated by numerical studies of small model systems. Two numerical methods were used: the worldline quantum Monte Carlo method with a loop cluster algorithm (QMC) and the finite-temperature Lanczos method (FTLM), yielding consistent results. The diamagnetic susceptibility introduced by coupling of the magnetic field to the orbital current reveals an anomalous temperature dependence, changing character from diamagnetic to paramagnetic at intermediate temperatures.

cond-mat.str-el↗

arXiv2000

Thermodynamic and diamagnetic properties of weakly doped antiferromagnets

Finite-temperature properties of weakly doped antiferromagnets as modeled by the two-dimensional t-J model and relevant to underdoped cuprates are investigated by numerical studies of small model systems at low doping. Two numerical methods are used: the worldline quantum Monte Carlo method with a loop cluster algorithm and the finite-temperature Lanczos method, yielding consistent results. Thermodynamic quantities: specific heat, entropy and spin susceptibility reveal a sizeable perturbation induced by holes introduced into a magnetic insulator, as well as a pronounced temperature dependence. The diamagnetic susceptibility introduced by coupling of the magnetic field to the orbital current reveals an anomalous temperature dependence, changing character from diamagnetic to paramagnetic at intermediate temperatures.

cond-mat.str-el↗

arXiv1998

Spin polaron in a magnetic field

The influence of the homogeneous magnetic field on a single mobile hole in a magnetic insulator, as represented by the two-dimensional t-J model, is investigated by considering the coupling of the field to the orbital current. The energy of the J=0 system is analysed via the high-temperature expansion and the small system diagonalization. The susceptibility is shown to be diamagnetic and diverging at low temperatures T. In contrast, in the antiferrmagnetic J>0 case small systems generically reveal a tendency towards a paramagnetic response in larger fields at low T. By employing at T=0 the cumulant expansion we study the ground state in arbitrary B, showing a behavior very sensitive to the character of the quasiparticle dispersion and the magnetic-field strength. At low B the perturbation and small-systems results are consistent with a pronounced diamagnetic susceptibility at T->0, but indicate on a suppressed contribution at intermediate T~J.

cond-mat.str-el↗