1,919 research outputs found
Arrival Directions of Cosmic Rays above 32 EeV from Phase One of the Pierre Auger Observatory
A promising energy range to look for angular correlations between cosmic rays of extragalactic origin and their sources is at the highest energies, above a few tens of EeV (1 EeV ⥠1018 eV). Despite the flux of these particles being extremely low, the area of âŒ3000 km2 covered at the Pierre Auger Observatory, and the 17 yr data-taking period of the Phase 1 of its operations, have enabled us to measure the arrival directions of more than 2600 ultrahigh-energy cosmic rays above 32 EeV. We publish this data set, the largest available at such energies from an integrated exposure of 122,000 km2 sr yr, and search it for anisotropies over the 3.4Ï steradians covered with the Observatory. Evidence for a deviation in excess of isotropy at intermediate angular scales, with âŒ15° Gaussian spread or âŒ25° top-hat radius, is obtained at the 4Ï significance level for cosmic-ray energies above âŒ40 EeV.Fil: Abreu, P.. Instituto Superior Tecnico; Portugal. Universidade Nova de Lisboa; PortugalFil: Aglietta, M.. Istituto Nazionale di Astrofisica; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Albury, J.M.. University of Adelaide; AustraliaFil: Allekotte, Ingomar. ComisiĂłn Nacional de EnergĂa AtĂłmica. Gerencia del Ărea de EnergĂa Nuclear. Instituto Balseiro; ArgentinaFil: Mollerach, Maria Silvia. ComisiĂłn Nacional de EnergĂa AtĂłmica. Gerencia del Ărea de EnergĂa Nuclear. Instituto Balseiro. Archivo HistĂłrico del Centro AtĂłmico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo HistĂłrico del Centro AtĂłmico Bariloche e Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Almeida Cheminant, K.. Polish Academy Of Sciences; PoloniaFil: Zapparrata, O.. UniversitĂ© Libre de Bruxelles; BĂ©lgicaFil: Zas, E.. Universidad de Santiago de Compostela; EspañaFil: Zavrtanik, D.. University of Nova Gorica; Eslovaquia. Experimental Particle Physics Department; EslovaquiaFil: Zavrtanik, M.. University of Nova Gorica; Eslovaquia. Experimental Particle Physics Department; EslovaquiaFil: Zehrer, L.. University of Nova Gorica; Eslovaqui
Measurement of Aerosols at the Pierre Auger Observatory
The air fluorescence detectors (FDs) of the Pierre Auger Observatory are
vital for the determination of the air shower energy scale. To compensate for
variations in atmospheric conditions that affect the energy measurement, the
Observatory operates an array of monitoring instruments to record hourly
atmospheric conditions across the detector site, an area exceeding 3,000 square
km. This paper presents results from four instruments used to characterize the
aerosol component of the atmosphere: the Central Laser Facility (CLF), which
provides the FDs with calibrated laser shots; the scanning backscatter lidars,
which operate at three FD sites; the Aerosol Phase Function monitors (APFs),
which measure the aerosol scattering cross section at two FD locations; and the
Horizontal Attenuation Monitor (HAM), which measures the wavelength dependence
of aerosol attenuation.Comment: Contribution to the 30th International Cosmic Ray Conference, Merida
Mexico, July 2007; 4 pages, 4 figure
The Lidar System of the Pierre Auger Observatory
The Pierre Auger Observatory in Malargue, Argentina, is designed to study the origin of ultrahigh energy cosmic rays with energies above 10^18 eV. The energy calibration of the detector is based on a system of four air fluorescence detectors. To obtain reliable calorimetric information from the fluorescence stations, the atmospheric conditions at the experiment's site need to be monitored continuously during operation. One of the components of the observatory's atmospheric monitoring system is a set of four elastic backscatter lidar stations, one station at each of the fluorescence detector sites. This paper describes the design, current status, standard operation procedure, and performance of the lidar system of the Pierre Auger Observatory
Angular Dependence of Neutrino Flux in KM3 Detectors in Low Scale Gravity Models
Cubic kilometer neutrino telescopes are capable of probing fundamental
questions of ultra-high energy neutrino interactions. There is currently great
interest in neutrino interactions caused by low-scale, extra dimension models.
Above 1 PeV the cross section in low scale gravity models rises well above the
total Standard Model cross section. We assess the observability of this effect
in the 1 PeV - 100 PeV energy range of kilometer-scale detectors with several
new points of emphasis that hinge on enhanced neutral current cross sections. A
major point is the importance of ``feed-down'' regeneration of upward neutrino
flux, driven by new-physics neutral current interactions in the flux evolution
equations. Feed-down is far from negligible, and it is essential to include its
effect. We then find that the angular distribution of events has high
discriminating value in separating models. In particular the ``up-to-down''
ratio between upward and downward-moving neutrino fluxes is a practical
diagnostic tool which can discriminate between models in the near future. The
slope of the angular distribution, in the region of maximum detected flux, is
also substantially different in low-scale gravity and the Standard Model. These
observables are only weakly dependent on astrophysical flux uncertainties. We
conclude that angular distributions can reveal a breakdown of the Standard
Model and probe the new physics beyond, as soon as data become available.Comment: 25 pages, 6 figures, discussion of calculations expanded, references
adde
Extensive air showers with TeV-scale quantum gravity
One of the possible consequences of the existence of extra degrees of freedom
beyond the electroweak scale is the increase of neutrino-nucleon cross sections
() beyond Standard Model predictions. At ultra-high energies
this may allow the existence of neutrino-initiated extensive air showers. In
this paper, we examine the most relevant observables of such showers. Our
analysis indicates that the future Pierre Auger Observatory could be
potentially powerful in probing models with large compact dimensions.Comment: 7 pages revtex, 5 eps fig
Tests of the Equivalence Principle with Neutral Kaons
We test the Principle of Equivalence for particles and antiparticles, using
CPLEAR data on tagged K0 and K0bar decays into pi^+ pi^-. For the first time,
we search for possible annual, monthly and diurnal modulations of the
observables |eta_{+-}| and phi_{+-}, that could be correlated with variations
in astrophysical potentials. Within the accuracy of CPLEAR, the measured values
of |eta_{+-}| and phi_{+-} are found not to be correlated with changes of the
gravitational potential. We analyze data assuming effective scalar, vector and
tensor interactions, and we conclude that the Principle of Equivalence between
particles and antiparticles holds to a level of 6.5, 4.3 and 1.8 x 10^{-9},
respectively, for scalar, vector and tensor potentials originating from the Sun
with a range much greater than the distance Earth-Sun. We also study
energy-dependent effects that might arise from vector or tensor interactions.
Finally, we compile upper limits on the gravitational coupling difference
between K0 and K0bar as a function of the scalar, vector and tensor interaction
range.Comment: 15 pages latex 2e, five figures, one style file (cernart.csl)
incorporate
Calibration of the Logarithmic-Periodic Dipole Antenna (LPDA) Radio Stations at the Pierre Auger Observatory using an Octocopter
An in-situ calibration of a logarithmic periodic dipole antenna with a
frequency coverage of 30 MHz to 80 MHz is performed. Such antennas are part of
a radio station system used for detection of cosmic ray induced air showers at
the Engineering Radio Array of the Pierre Auger Observatory, the so-called
Auger Engineering Radio Array (AERA). The directional and frequency
characteristics of the broadband antenna are investigated using a remotely
piloted aircraft (RPA) carrying a small transmitting antenna. The antenna
sensitivity is described by the vector effective length relating the measured
voltage with the electric-field components perpendicular to the incoming signal
direction. The horizontal and meridional components are determined with an
overall uncertainty of 7.4^{+0.9}_{-0.3} % and 10.3^{+2.8}_{-1.7} %
respectively. The measurement is used to correct a simulated response of the
frequency and directional response of the antenna. In addition, the influence
of the ground conductivity and permittivity on the antenna response is
simulated. Both have a negligible influence given the ground conditions
measured at the detector site. The overall uncertainties of the vector
effective length components result in an uncertainty of 8.8^{+2.1}_{-1.3} % in
the square root of the energy fluence for incoming signal directions with
zenith angles smaller than 60{\deg}.Comment: Published version. Updated online abstract only. Manuscript is
unchanged with respect to v2. 39 pages, 15 figures, 2 table
Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
We report a multi-resolution search for anisotropies in the arrival
directions of cosmic rays detected at the Pierre Auger Observatory with local
zenith angles up to and energies in excess of 4 EeV ( eV). This search is conducted by measuring the angular power spectrum
and performing a needlet wavelet analysis in two independent energy ranges.
Both analyses are complementary since the angular power spectrum achieves a
better performance in identifying large-scale patterns while the needlet
wavelet analysis, considering the parameters used in this work, presents a
higher efficiency in detecting smaller-scale anisotropies, potentially
providing directional information on any observed anisotropies. No deviation
from isotropy is observed on any angular scale in the energy range between 4
and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no
other deviation from isotropy is observed for moments beyond the dipole one.
The corresponding -values obtained after accounting for searches blindly
performed at several angular scales, are in the case of
the angular power spectrum, and in the case of the needlet
analysis. While these results are consistent with previous reports making use
of the same data set, they provide extensions of the previous works through the
thorough scans of the angular scales.Comment: Published version. Added journal reference and DOI. Added Report
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Ultrahigh-energy neutrino follow-up of Gravitational Wave events GW150914 and GW151226 with the Pierre Auger Observatory
On September 14, 2015 the Advanced LIGO detectors observed their first
gravitational-wave (GW) transient GW150914. This was followed by a second GW
event observed on December 26, 2015. Both events were inferred to have arisen
from the merger of black holes in binary systems. Such a system may emit
neutrinos if there are magnetic fields and disk debris remaining from the
formation of the two black holes. With the surface detector array of the Pierre
Auger Observatory we can search for neutrinos with energy above 100 PeV from
point-like sources across the sky with equatorial declination from about -65
deg. to +60 deg., and in particular from a fraction of the 90% confidence-level
(CL) inferred positions in the sky of GW150914 and GW151226. A targeted search
for highly-inclined extensive air showers, produced either by interactions of
downward-going neutrinos of all flavors in the atmosphere or by the decays of
tau leptons originating from tau-neutrino interactions in the Earth's crust
(Earth-skimming neutrinos), yielded no candidates in the Auger data collected
within s around or 1 day after the coordinated universal time (UTC)
of GW150914 and GW151226, as well as in the same search periods relative to the
UTC time of the GW candidate event LVT151012. From the non-observation we
constrain the amount of energy radiated in ultrahigh-energy neutrinos from such
remarkable events.Comment: Published version. Added journal reference and DOI. Added Report
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