311. 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, original scientific article Abstract: 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.
Keywords: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, extensive air showers, Auger Surface Detector signals risetime, azimuthal symmetry
Published in RUNG: 15.04.2016; Views: 6797; Downloads: 0
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312. Prospects for Measuring the Positron Excess with the Cherenkov Telescope ArrayJustin Vandenbroucke, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Keywords: Cherenkov Telescope Array (CTA), sensitivity, background rejection, silicon photomultipliers, cosmic rays, positron excess, Earth-Moon spectrometer
Published in RUNG: 14.03.2016; Views: 5539; Downloads: 228
 Full text (229,59 KB) |
313. 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, published scientific conference contribution Abstract: 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.
Keywords: Ultra-High Energy Cosmic Rays, Pierre Auger Observatory, Telescope Array, extensive air showers, secondary cosmic rays, muonic shower component, surface detectors
Published in RUNG: 08.03.2016; Views: 6026; Downloads: 191
Full text (1,42 MB) |
314. Large-Scale Distribution of Arrival Directions of Cosmic Rays Detected at the Pierre Auger Observatory and the Telescope Array above 10[sup]19 eVOlivier Deligny, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Abstract: The large-scale distribution of arrival directions of
high-energy cosmic rays is a key observable in attempts to
understanding their origin. The dipole and quadrupole moments
are of special interest in revealing potential anisotropies.
An unambiguous measurement of these moments as well as
of the full set of spherical harmonic coefficients requires
full-sky coverage. This can be achieved by combining data from
observatories located in both the northern and southern
hemispheres. To this end, a joint analysis using data recorded
at the Pierre Auger Observatory and the Telescope Array above
10[sup]19 eV has been performed. Thanks to the full-sky
coverage, the measurement of the dipole moment reported in
this study does not rely on any assumption on the underlying
flux of cosmic rays. As well, the resolution on the quadrupole
and higher order moments is the best ever obtained. The
resulting multipolar expansion of the flux of cosmic rays
allows a series of anisotropy searches to be performed,
and in particular to report on the first angular power
spectrum of cosmic rays. This allows a comprehensive
description of the angular distribution of cosmic rays
above 10[sup]19 eV.
Keywords: Pierre Auger Observatory, Telescope Array, high-energy cosmic rays, large-scale anisotropies, angular power spectrum
Published in RUNG: 08.03.2016; Views: 5932; Downloads: 193
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315. 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, published scientific conference contribution Abstract: 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.
Keywords: Pierre Auger Observatory, Telescope Array, Ultra-High Energy Cosmic Rays, elemental composition, extensive air showers, the atmospheric depth of the air shower maximum
Published in RUNG: 08.03.2016; Views: 5873; Downloads: 238
Full text (329,86 KB) |
316. 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, published scientific conference contribution Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, Telescope Array, high-energy neutrinos, IceCube, correlation search
Published in RUNG: 08.03.2016; Views: 6202; Downloads: 197
Full text (1,11 MB) |
317. Education, Outreach and Public Relations of the Pierre Auger ObservatoryCharles Timmermans, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Abstract: The scale and scope of the physics studied at the Pierre Auger
Observatory continue to offer significant opportunities for
original outreach work. Education, outreach and public
relations of the Auger Collaboration are coordinated in a
dedicated task whose goals are to encourage and support
a wide range of efforts that link schools and the public with
the Auger scientists and the science of cosmic rays, particle
physics, and associated technologies. We focus on the impact of
the Collaboration in Mendoza Province, Argentina and beyond.
The Auger Visitor Center in Malargüe has hosted over 95,000
visitors since 2001, and a fifth Collaboration-sponsored
science fair was held on the Observatory campus in November
2014. The Rural Schools Program, which is run by Observatory
staff and which brings cosmic-ray science and infrastructure
improvements to remote schools, continues to broaden its
reach. Numerous online resources, video documentaries, and
animations of extensive air showers have been created for wide
public release. Increasingly, collaborators draw on these
resources to develop Auger related displays and outreach events
at their institutions and in public settings to disseminate the
science and successes of the Observatory worldwide. We also
highlight education and outreach activities associated with the
planned upgrade of the Observatory’s detector systems and
future physics goals.
Keywords: Pierre Auger Observatory, cosmic rays physics, education, outreach, public relations
Published in RUNG: 03.03.2016; Views: 6286; Downloads: 187
Full text (4,12 MB) |
318. 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, published scientific conference contribution Abstract: 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.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, elemental composition sensitivity, Auger upgrade (AugerPrime), muonic shower component, scintillator detectors
Published in RUNG: 03.03.2016; Views: 5647; Downloads: 226
Full text (659,02 KB) |
319. Solar Cycle Modulation of Cosmic Rays Observed with the Low Energy Modes of the Pierre Auger ObservatoryJimmy Masías-Meza, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Abstract: The low energy modes of the surface detector array of the
Pierre Auger Observatory record variations in the flux of low
energy secondary particles with extreme detail. These two modes
consist of recording (1) the rate of signals for energies
between ∼15 MeV and ∼100 MeV (the Scaler mode) and (2) the
calibration charge histograms of the individual pulses detected
by each water-Cherenkov station, covering different energy
channels up to ∼1 GeV (the Histogram mode). Previous work has
studied the flux of galactic cosmic rays on short and
intermediate time scales (i.e. from minutes to weeks) using
these low energy modes. In this work, after including a long-
term correction to the response of the detectors, we present
the first long-term analysis of the flux of cosmic rays using
scalers and two energy bands of the calibration histograms.
We show its sensitivity to the solar cycle variation and its
relation to the solar modulation of cosmic rays for an 8-year
period.
Keywords: Pierre Auger Observatory, Surface Detector, secondary cosmic rays, scaler mode, charge histogram mode, solar cycle modulation
Published in RUNG: 03.03.2016; Views: 6189; Downloads: 209
Full text (533,18 KB) |
320. 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, published scientific conference contribution Abstract: 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.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, energy spectrum, elemental composition, combined data fit
Published in RUNG: 03.03.2016; Views: 5917; Downloads: 234
Full text (704,98 KB) |
