11. Mass composition of ultra-high energy cosmic rays at the Pierre Auger ObservatoryGašper Kukec Mezek, 2019, doktorska disertacija 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: 5017; Prenosov: 187 Celotno besedilo (17,53 MB) |
12. Depth of maximum of air-shower profiles at the Pierre Auger Observatory: Measurements above 10^17.2 eV and Composition ImplicationsJosé Bellido, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2017, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, depth of maximum of air-shower, mass composition Objavljeno v RUNG: 16.02.2018; Ogledov: 3183; Prenosov: 143 Celotno besedilo (1,19 MB) |
13. Results from the Pierre Auger ObservatoryIvan De Mitri, Andrej Filipčič, Samo Stanič, Darko Veberič, Danilo Zavrtanik, Marko Zavrtanik, 2015, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, Ultra High Energy Cosmic Rays (UHECR), UHECR energy spectrum, UHECR mass composition Objavljeno v RUNG: 27.06.2017; Ogledov: 4203; Prenosov: 0 Gradivo ima več datotek! Več... |
14. 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, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), UHECR energy spectrum, mass composition, anisotropies Objavljeno v RUNG: 20.06.2017; Ogledov: 4966; Prenosov: 0 Gradivo ima več datotek! Več... |
15. 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, objavljeni znanstveni prispevek na konferenci Ključne besede: Pierre Auger Observatory, ultra high energy cosmic rays (UHECR), UHECR hybrid detection technique, UHECR energy spectrum, UHECR mass composition, UHECR arrival directions Objavljeno v RUNG: 20.06.2017; Ogledov: 5220; Prenosov: 395 Celotno besedilo (861,47 KB) |
16. 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, izvirni znanstveni članek Ključne besede: 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 Objavljeno v RUNG: 25.11.2016; Ogledov: 4786; Prenosov: 180 Celotno besedilo (1,73 MB) |
17. 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, objavljeni znanstveni prispevek na konferenci Ključne besede: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, Telescope Array, cross-calibration studies Objavljeno v RUNG: 17.11.2016; Ogledov: 5307; Prenosov: 0 Gradivo ima več datotek! Več... |
18. 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, objavljeni znanstveni prispevek na konferenci Ključne besede: ultra-high energy cosmic rays (UHECR), Pierre Auger Observatory, UHECR mass composition Objavljeno v RUNG: 09.11.2016; Ogledov: 4556; Prenosov: 236 Celotno besedilo (1,24 MB) |
19. Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger ObservatoryA. Aab, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2016, izvirni znanstveni članek Opis: The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable, (secθ)max, sensitive to the mass composition of cosmic rays above 3×1018 eV. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass increases slowly with energy, as has been inferred from other studies. However, the mass estimates are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modeling that must be resolved before the mass composition can be inferred from (secθ)max. Ključne besede: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, extensive air showers, Auger Surface Detector signals risetime, azimuthal symmetry Objavljeno v RUNG: 15.04.2016; Ogledov: 5508; Prenosov: 0 Gradivo ima več datotek! Več... |
20. Measurement of the muon content in air showers at the Pierre Auger ObservatoryLaura Collica, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2015, objavljeni znanstveni prispevek na konferenci Opis: The muon content of extensive air showers is an
observable sensitive to the primary composition and to
the hadronic interaction properties. We present here
different methods which allow us to estimate the muon number
at the ground level and the muon production depth by
exploiting the measurement of the longitudinal, lateral and
temporal distribution of particles in air showers recorded at
the Pierre Auger Observatory. The results, obtained at about
10[sup]19 eV (E[inf]CM ∼ 140 TeV center-of-mass energy for
proton primaries), are compared to the predictions
of LHC-tuned hadronic interaction models with different primary
masses and suggest a deficit in the muon content at the
ground predicted by simulations. The Pierre Auger Observatory
uses water-Cherenkov detectors to measure particle
densities at the ground and therefore has a good
sensitivity to the muon content of air showers. Moreover, due
to its hybrid design, the combination of muon measurements with
other independent mass composition analyses such as Xmax
provides additional constraints on hadronic interaction models. Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, muons, mass composition, hadronic interactions Objavljeno v RUNG: 03.03.2016; Ogledov: 4817; Prenosov: 218 Celotno besedilo (298,46 KB) |