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Opis: Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.
Ključne besede: Ultra-High Energy Cosmic Rays, Cosmic ray composition, Atmospheric fluorescence, Extensive air shower array, Hybrid, Telescope Array
Objavljeno v RUNG: 24.04.2020; Ogledov: 3043; Prenosov: 0
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Opis: Ultra-high-energy cosmic rays (UHECRs) are highly energetic particles with EeV energies, exceeding the capabilities of man-made colliders. They hold information on extreme astrophysical processes that create them and the medium they traverse on their way towards Earth. However, their mass composition at such energies is still unclear, because data interpretation depends on our choice of high energy hadronic interaction models. With its hybrid detection method, the Pierre Auger Observatory has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations (SD) and fluorescence telescopes (FD). We present recent mass composition results from the Pierre Auger Collaboration using observational parameters from SD and FD measurements. Using the full dataset of the Pierre Auger Observatory, implications on composition can be made for energies above 10^17.2 eV.
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Objavljeno v RUNG: 24.05.2019; Ogledov: 3423; Prenosov: 110
Celotno besedilo (573,00 KB)

Opis: Cosmic rays with energies above 10^18 eV, usually referred to as ultra-high energy cosmic rays (UHECR), have been a mystery from the moment they have been discovered. Although we have now more information on their extragalactic origin, their direct sources still remain hidden due to deviations caused by galactic magnetic fields. Another mystery, apart from their production sites, is their nature. Their mass composition, still uncertain at these energies, would give us a better understanding on their production, acceleration, propagation and capacity to produce extensive air showers in the Earth's atmosphere. Mass composition studies of UHECR try to determine their nature from the difference in development of their extensive air showers. In this work, observational parameters from the hybrid detection system of the Pierre Auger Observatory are used in a multivariate analysis to obtain the mass composition of UHECR. The multivariate analysis (MVA) approach combines a number of mass composition sensitive variables and tries to improve the separation between different UHECR particle masses. Simulated distributions of different primary particles are fitted to measured observable distributions in order to determine individual elemental fractions of the composition. When including observables from the surface detector, we find a discrepancy in the estimated mass composition between a mixed simulation sample and the Pierre Auger data. Our analysis results from the Pierre Auger data are to a great degree independent on hadronic interaction models. Although they differ at higher primary masses, the different models are more consistent, when combining fractions of oxygen and iron. Compared to previously published results, the systematic uncertainty from hadronic interaction models is roughly four times smaller. Our analysis reports a predominantly heavy composition of UHECR, with more than a 50% fraction of oxygen and iron at low energies. The composition is then becoming heavier with increasing energy, with a fraction of oxygen and iron above 80% at the highest energies.
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, machine learning, multivariate analysis
Objavljeno v RUNG: 03.04.2019; Ogledov: 5016; Prenosov: 187
Celotno besedilo (17,53 MB)

Ključne besede: ultra-high-energy photons, Pierre Auger Observatory, hybrid detector
Objavljeno v RUNG: 16.02.2018; Ogledov: 3265; Prenosov: 149
Celotno besedilo (383,49 KB)

Opis: The Pierre Auger Observatory (PAO), the world’s largest cosmic ray detector combines a large surface detector (SD) with an air fluorescence detector (FD). It is designed to observe extensive air showers (EAS) of billions of secondary particles induced by the UHECRs in the earths’ atmosphere. The “hybrid” design (i.e., detected simultaneously by SD and FD) provides wealth of information about shower development and excellent event reconstruction. Together with observations of UHECRs, the Surface Detector (SD) of the PAO is sensitive to UHE neutrinos through the observation of deeply initiated inclined down-going showers produced by neutrino interactions in the atmosphere, which method has been well established. On the other hand, high-energy photons can also be discriminated from background of charged cosmic rays based on their characters of the shower front. In this talk, I will give a review on recent results from PAO and introduce the ultra-high energy multi-messenger studies from PAO.
Ključne besede: Pierre Auger Observatory, cosmic rays, ultra-high energy
Objavljeno v RUNG: 17.01.2018; Ogledov: 3811; Prenosov: 0
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