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71.
Fermi -LAT Observations of LIGO / Virgo Event GW170817
Gabrijela Zaharijas, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...gamma-ray burst, gamma rays, gravitational waves...
Ključne besede: gamma-ray burst, gamma rays, gravitational waves
Objavljeno: 23.08.2018; Ogledov: 2291; Prenosov: 0
.pdf Polno besedilo (5,09 MB)

72.
The Search for Spatial Extension in High-latitude Sources Detected by the Fermi Large Area Telescope
Gabrijela Zaharijas, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...BL Lacertae objects, gamma rays, ISM: H II Regions, ISM: supernova remnants...
Ključne besede: BL Lacertae objects, gamma rays, ISM: H II Regions, ISM: supernova remnants
Objavljeno: 23.08.2018; Ogledov: 2319; Prenosov: 0
.pdf Polno besedilo (6,39 MB)

73.
Millisecond Pulsar Origin of the Galactic Center Excess and Extended Gamma-Ray Emission from Andromeda: A Closer Look
Christopher Eckner, Gabrijela Zaharijas, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...gamma rays: galaxies – Local Group – pulsars: general...
Ključne besede: gamma rays: galaxies – Local Group – pulsars: general
Objavljeno: 24.08.2018; Ogledov: 2500; Prenosov: 0
.pdf Polno besedilo (846,36 KB)

74.
A gamma-ray determination of the Universe ’ s star formation history
Gabrijela Zaharijas, Marco Ajello, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...gamma rays, Fermi LAT, Extragalactic Background LIght...
Ključne besede: gamma rays, Fermi LAT, Extragalactic Background LIght
Objavljeno: 05.12.2018; Ogledov: 2099; Prenosov: 0
.pdf Polno besedilo (488,29 KB)

75.
Unresolved Gamma-Ray Sky through its Angular Power Spectrum
Gabrijela Zaharijas, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...gamma rays, Fermi LAT, isotropic emission...
Ključne besede: gamma rays, Fermi LAT, isotropic emission
Objavljeno: 20.12.2018; Ogledov: 2009; Prenosov: 0
.pdf Polno besedilo (591,09 KB)

76.
Multi-Messenger Physics With the Pierre Auger Observatory
Karl-Heinz Kampert, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...Pierre Auger Observatory, ultra-high energy cosmic rays, photons, neutrinos, protons, multi-messenger physics and astrophysics...
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, photons, neutrinos, protons, multi-messenger physics and astrophysics
Objavljeno: 06.05.2019; Ogledov: 2103; Prenosov: 86
.pdf Polno besedilo (2,46 MB)

77.
Mass composition of ultra-high energy cosmic rays at the Pierre Auger Observatory
Gašper 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.
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, machine learning, multivariate analysis
Objavljeno: 03.04.2019; Ogledov: 3110; Prenosov: 139
.pdf Polno besedilo (17,53 MB)

78.
SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORY
Marta Trini, 2019, doktorska disertacija

Opis: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory is the largest experiment that can detect the extensive air showers produced when the cosmic rays and neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply- penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We have established a complete chain of criteria to first select the inclined events among the sample of all events triggering the Infilled array, and then identifying those that have a large electromagnetic component at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017. Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor, k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Najdeno v: ključnih besedah
Povzetek najdenega: ...of the origin of the UHE cosmic rays. The Pierre Auger Observatory is the largest experiment...
Ključne besede: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled array
Objavljeno: 03.10.2019; Ogledov: 3182; Prenosov: 103
.pdf Polno besedilo (6,02 MB)

79.
Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser
Giovanni De Ninno, Primož Rebernik Ribič, 2019, izvirni znanstveni članek

Opis: X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths.
Najdeno v: ključnih besedah
Povzetek najdenega: ...of the electron beam before emission of X- rays. We demonstrate high-gain EEHG lasing producing stable,...
Ključne besede: free electron laser, coherence, x-rays
Objavljeno: 07.05.2019; Ogledov: 2111; Prenosov: 0
.pdf Polno besedilo (6,89 MB)

80.
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 Observatory
Gašper Kukec Mezek, 2018, objavljeni znanstveni prispevek na konferenci

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.
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Objavljeno: 24.05.2019; Ogledov: 2220; Prenosov: 86
.pdf Polno besedilo (573,00 KB)

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