41. Eenergy Anisotropies of Proton-like Ultra-High Energy Cosmic RaysJon Paul Lundquist, doctoral dissertation Abstract: Evidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA “Hotspot” excess, E≥10^19.75 eV, is found to correspond to a deficit, or “Coldspot,” of events for 10^19.1≤E<10^19.75 eV at 142◦R.A., 40◦ Dec. The global post-trial significance of this Hot/Coldspot event density asymmetry is found to be 5.1σ (p = 1.56 × 10−7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74σ significance for energies E≥10^19.2 eV and an energy-distance correlation with a 3.34σ significance for energies E≥1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65σ significance (E≥1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new “Quality Factor Analysis” pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean shower depth distribution is developed – as there is large disagreement in between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E≥10^18.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields. Keywords: cosmic rays, UHECR, composition, anisotropy Published in RUNG: 24.04.2020; Views: 2869; Downloads: 0 This document has many files! More... |
42. Mass composition of cosmic rays with energies from 10^17.2 eV to 10^20 eV using surface and fluorescence detectors of the Pierre Auger ObservatoryGašper Kukec Mezek, 2018, published scientific conference contribution Abstract: 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. Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations Published in RUNG: 24.05.2019; Views: 3363; Downloads: 110 Full text (573,00 KB) |
43. Mass composition of ultra-high energy cosmic rays at the Pierre Auger ObservatoryGašper Kukec Mezek, 2019, doctoral dissertation Abstract: 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. Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, machine learning, multivariate analysis Published in RUNG: 03.04.2019; Views: 4941; Downloads: 186 Full text (17,53 MB) |
44. A Monte Carlo simulation study for cosmic-ray chemical composition measurement with Cherenkov Telescope ArrayMichiko Ohishi, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: CTA, Monte Carlo simulation, cosmic-ray chemical composition Published in RUNG: 16.02.2018; Views: 3776; Downloads: 142 Full text (448,16 KB) |
45. Results from the Pierre Auger ObservatoryIvan De Mitri, Andrej Filipčič, Samo Stanič, Darko Veberič, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Keywords: Pierre Auger Observatory, Ultra High Energy Cosmic Rays (UHECR), UHECR energy spectrum, UHECR mass composition Published in RUNG: 27.06.2017; Views: 4138; Downloads: 0 This document has many files! More... |
46. Astroparticles at the High Energy Frontier: Results from the Pierre Auger ObservatoryGonzalo Parente, Andrej Filipčič, Ahmed Saleh, Samo Stanič, Darko Veberič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2014, published scientific conference contribution Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), UHECR energy spectrum, mass composition, anisotropies Published in RUNG: 20.06.2017; Views: 4896; Downloads: 0 This document has many files! More... |
47. Auger HighlightsAntonella Castellina, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2014, published scientific conference contribution Keywords: Pierre Auger Observatory, ultra high energy cosmic rays (UHECR), UHECR hybrid detection technique, UHECR energy spectrum, UHECR mass composition, UHECR arrival directions Published in RUNG: 20.06.2017; Views: 5133; Downloads: 395 Full text (861,47 KB) |
48. Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrumA. Aab, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2016, original scientific article Keywords: ultra-high energy cosmic rays (UHECR), UHECR mass composition, UHECR energy spectrum, Pierre Auger Observatory, composition studies at the ‘ankle’ region in the UHECR spectrum Published in RUNG: 25.11.2016; Views: 4727; Downloads: 180 Full text (1,73 MB) |
49. Report of the Working Group on the Composition of Ultra High Energy Cosmic RaysR. Abbasi, Andrej Filipčič, Ahmed Saleh, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2016, published scientific conference contribution Keywords: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, Telescope Array, cross-calibration studies Published in RUNG: 17.11.2016; Views: 5239; Downloads: 0 This document has many files! More... |
50. Measurement of the mass composition of ultra-high energy cosmic rays with the Pierre Auger ObservatoryMariangela Settimo, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2016, published scientific conference contribution Keywords: ultra-high energy cosmic rays (UHECR), Pierre Auger Observatory, UHECR mass composition Published in RUNG: 09.11.2016; Views: 4486; Downloads: 236 Full text (1,24 MB) |