191. 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: 5622; Prenosov: 0 Gradivo ima več datotek! Več... |
192. Initial results of a direct comparison between the Surface Detectors of the Pierre Auger Observatory and the Telescope ArrayR. Takeishi, 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 Pierre Auger Observatory (Auger) in Mendoza, Argentina and
the Telescope Array (TA) in Utah, USA aim at unraveling the
origin and nature of Ultra-High Energy Cosmic Rays (UHECR).
At present, there appear to be subtle differences between Auger
and TA results and interpretations. Joint working groups have
been established and have already reported preliminary
findings. From an experimental standpoint, the Surface
Detectors (SD) of both experiments make use of different
detection processes not equally sensitive to the components of
the extensive air showers making it to the ground. In particular, the muonic component of the shower measured at
ground level can be traced back to the primary composition,
which is critical for understanding the origin of UHECRs.
In order to make direct comparisons between the SD detection
techniques used by Auger and TA, a joint SD experimental
research program is being developed. In the first phase,
two Auger SD stations were deployed at the TA Central Laser
Facility to compare station-level responses. This paper
concentrates on the results obtained with the first Auger SD
station (an “Auger North” design), which has been operating
since October 2014. The second Auger SD station, identical to
the ones being operated at Auger in Argentina (an “Auger South”
design), was just deployed in June 2015. The second phase of
this research program will be to co-locate six Auger North SD
stations with TA stations in the field to compare event-level
responses. Ključne besede: Ultra-High Energy Cosmic Rays, Pierre Auger Observatory, Telescope Array, extensive air showers, secondary cosmic rays, muonic shower component, surface detectors Objavljeno v RUNG: 08.03.2016; Ogledov: 4889; Prenosov: 188 Celotno besedilo (1,42 MB) |
193. Report of the Working Group on the Composition of Ultra-High Energy Cosmic RaysMichael Unger, 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 atmospheric depth, Xmax, at which the particle number of
an air shower reaches its maximum is a good indicator for the
mass of the primary particle. We present a comparison of the
energy evolution of the mean of Xmax as measured by the
Telescope Array and c Collaborations. After
accounting for the different resolutions, acceptances and
analysis strategies of the two experiments, the two results are
found to be in good agreement within systematic uncertainties. Ključne besede: Pierre Auger Observatory, Telescope Array, Ultra-High Energy Cosmic Rays, elemental composition, extensive air showers, the atmospheric depth of the air shower maximum Objavljeno v RUNG: 08.03.2016; Ogledov: 4832; Prenosov: 235 Celotno besedilo (329,86 KB) |
194. Search for a correlation between the UHECRs measured by the Pierre Auger Observatory and the Telescope Array and the neutrino candidate events from IceCubeAsen Christov, 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: We have conducted three searches for correlations between
ultra-high energy cosmic rays detected by the Telescope Array
and the Pierre Auger Observatory, and high-energy neutrino
candidate events from IceCube. Two cross-correlation analyses
with UHECRs are done: one with 39 cascades from the IceCube
‘high-energy starting events’ sample and the other with 16
high-energy ‘track events’. The angular separation between the
arrival directions of neutrinos and UHECRs is scanned over.
The same events are also used in a separate search using a
maximum likelihood approach, after the neutrino arrival
directions are stacked. To estimate the significance we assume
UHECR magnetic deflections to be inversely proportional to
their energy, with values 3◦, 6◦ and 9◦ at 100 EeV to allow for
the uncertainties on the magnetic field strength and UHECR
charge. A similar analysis is performed on stacked UHECR
arrival directions and the IceCube sample of through-going
muon track events which were optimized for neutrino point-
source searches. Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, Telescope Array, high-energy neutrinos, IceCube, correlation search Objavljeno v RUNG: 08.03.2016; Ogledov: 5100; Prenosov: 192 Celotno besedilo (1,11 MB) |
195. Upgrade of the Pierre Auger Observatory (AugerPrime)Ralph Engel, 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 data collected with the Pierre Auger Observatory have led
to a number of surprising discoveries. While a strong
suppression of the particle flux at the highest energies has
been established unambiguously, the dominant physics processes
related to this suppression could not be identified.
Within the energy range covered by fluorescence detector
observations with sufficient statistics, an unexpected change
of the depth of maximum distribution is found. Using LHC-tuned
interaction models these observations can be understood as a
correlated change of the fluxes of different mass groups.
On the other hand, they could also indicate a change of
hadronic interactions above the energy of the ankle.
Complementing the water Cherenkov detectors of the surface
array with scintillator detectors will, mainly through the
determination of the muonic shower component, extend the
composition sensitivity of the Auger Observatory into the flux
suppression region. The upgrade of the Auger Observatory will
allow us to estimate the primary mass of the highest energy
cosmic rays on a shower-by-shower basis. In addition to
measuring the mass composition the upgrade will open the
possibility to search for light primaries at the highest
energies, to perform composition-selected anisotropy studies,
and to search for new phenomena including unexpected changes
of hadronic interactions. After introducing the physics
motivation for upgrading the Auger Observatory the planned
detector upgrade is presented. In the second part
of the contribution the expected performance and improved
physics sensitivity of the upgraded Auger Observatory are
discussed. Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, elemental composition sensitivity, Auger upgrade (AugerPrime), muonic shower component, scintillator detectors Objavljeno v RUNG: 03.03.2016; Ogledov: 4571; Prenosov: 222 Celotno besedilo (659,02 KB) |
196. Combined fit of spectrum and composition data as measured by the Pierre Auger ObservatoryAndrea Di Matteo, 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: We present a combined fit of both flux and composition of
ultra-high energy cosmic rays as measured by the Pierre Auger
Observatory. The fit has been performed for energies above
5 × 10[sup]18 eV, i.e. the region of the all-particle spectrum
above the so-called “ankle” feature. A simple astrophysical model consisting of identical sources has been adopted, where
nuclei are injected with a rigidity dependent mechanism and the
sources are uniformly distributed in a comoving volume.
The fit results suggest a source model characterized by
relatively low maximum injection energies and hard spectral
indices. The impact of different sources of systematic
uncertainties in the above result is discussed. Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, energy spectrum, elemental composition, combined data fit Objavljeno v RUNG: 03.03.2016; Ogledov: 4766; Prenosov: 231 Celotno besedilo (704,98 KB) |
197. 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: 4923; Prenosov: 218 Celotno besedilo (298,46 KB) |
198. Update of the neutrino and photon limits from the Pierre Auger ObservatoryCarla Bleve, 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: Ultra-high energy neutrinos and photons, with energies above
1 EeV and 10 EeV respectively, can be detected with the Surface
Detector array (SD) of the Pierre Auger Observatory. Downward-
going neutrinos of all flavours interacting in the atmosphere
at zenith angles θ > 60◦, upward-going tau neutrinos (“Earth-
skimming”), as well as photons in the zenith range 30◦ − 60◦
can be identified through the broad time-structure of the
signals expected to be induced in the SD stations. An
additional signature for photon-induced air showers is the
steeper lateral distribution of secondary particles at ground
with respect to the nucleonic showers. Stringent limits are set
to the diffuse flux of ultra-high energy (UHE) neutrinos and
photons, using data collected between 2004 and mid-2013, under
the hypothesis of an E[sup]−2 spectrum for signal primaries. Ključne besede: ultra-high energy neutrinos, ultra-high energy photons, cosmic rays, elemental composition, Pierre Auger Observatory Objavljeno v RUNG: 03.03.2016; Ogledov: 5030; Prenosov: 234 Celotno besedilo (398,21 KB) |
199. Composition at the “ankle” measured by the Pierre Auger Observatory: pure or mixed?Alexey Yushkov, 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: We report for the first time on the measurement of the
correlation between the depth of shower maximum and the signal
in water-Cherenkov stations for events reconstructed by both
the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlated measurement is a unique feature
of a hybrid air-shower observatory and allows us to determine
the purity of the cosmic-ray composition. The observed
correlation in the energy range around the “ankle”
lg(E/eV) = 18.5−19.0 differs significantly from the expectations for pure beams, indicating that the primary composition in this range is mixed, unless the
hadronic interactions at these energies behave very
differently than in conventional, LHC-tuned event generators. Ključne besede: ultra-high energy cosmic rays, elemental composition, depth of shower maximum, secondary cosmic rays, Pierre Auger Observatory Objavljeno v RUNG: 02.03.2016; Ogledov: 5485; Prenosov: 238 Celotno besedilo (388,00 KB) |
200. Search for energy dependent patterns in the arrival direction of cosmic rays at the Pierre Auger ObservatoryTobias Winchen, 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: Energy-dependent patterns in the arrival directions of cosmic
rays are expected from deflections in galactic and extragalactic magnetic fields. We report on searches for such
patterns in the data of the surface detector of the Pierre
Auger Observatory at energies above E = 5 EeV in regions
within approximately 15◦ around events with energy E > 60
EeV. No significant patterns are found with this analysis which
can be used to constrain parameters in propagation scenarios. Ključne besede: ultra-high energy cosmic rays
galactic and extragalactic magnetic fields
magnetic deflection patterns
Pierre Auger Observatory Objavljeno v RUNG: 02.03.2016; Ogledov: 5513; Prenosov: 228 Celotno besedilo (1019,52 KB) |