20 research outputs found
Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight
The first flight of the Antarctic Impulsive Transient Antenna (ANITA)
experiment recorded 16 radio signals that were emitted by cosmic-ray induced
air showers. For 14 of these events, this radiation was reflected from the ice.
The dominant contribution to the radiation from the deflection of positrons and
electrons in the geomagnetic field, which is beamed in the direction of motion
of the air shower. This radiation is reflected from the ice and subsequently
detected by the ANITA experiment at a flight altitude of 36km. In this paper,
we estimate the energy of the 14 individual events and find that the mean
energy of the cosmic-ray sample is 2.9 EeV. By simulating the ANITA flight, we
calculate its exposure for ultra-high energy cosmic rays. We estimate for the
first time the cosmic-ray flux derived only from radio observations. In
addition, we find that the Monte Carlo simulation of the ANITA data set is in
agreement with the total number of observed events and with the properties of
those events.Comment: Added more explanation of the experimental setup and textual
improvement
Benford's law predicted digit distribution of aggregated income taxes: the surprising conformity of Italian cities and regions
The yearly aggregated tax income data of all, more than 8000, Italian
municipalities are analyzed for a period of five years, from 2007 to 2011, to
search for conformity or not with Benford's law, a counter-intuitive phenomenon
observed in large tabulated data where the occurrence of numbers having smaller
initial digits is more favored than those with larger digits. This is done in
anticipation that large deviations from Benford's law will be found in view of
tax evasion supposedly being widespread across Italy. Contrary to expectations,
we show that the overall tax income data for all these years is in excellent
agreement with Benford's law. Furthermore, we also analyze the data of
Calabria, Campania and Sicily, the three Italian regions known for strong
presence of mafia, to see if there are any marked deviations from Benford's
law. Again, we find that all yearly data sets for Calabria and Sicily agree
with Benford's law whereas only the 2007 and 2008 yearly data show departures
from the law for Campania. These results are again surprising in view of
underground and illegal nature of economic activities of mafia which
significantly contribute to tax evasion. Some hypothesis for the found
conformity is presented.Comment: 18 pages, 5 tables, 4 figures, 61 references, To appear in European
Physical Journal
Clusters of galaxies: setting the stage
Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun.
They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %)
and a small fraction of stars, dust, and cold gas, mostly locked in galaxies.
In most clusters, scaling relations between their properties testify that the
cluster components are in approximate dynamical equilibrium within the cluster
gravitational potential well. However, spatially inhomogeneous thermal and
non-thermal emission of the intracluster medium (ICM), observed in some
clusters in the X-ray and radio bands, and the kinematic and morphological
segregation of galaxies are a signature of non-gravitational processes, ongoing
cluster merging and interactions. In the current bottom-up scenario for the
formation of cosmic structure, clusters are the most massive nodes of the
filamentary large-scale structure of the cosmic web and form by anisotropic and
episodic accretion of mass. In this model of the universe dominated by cold
dark matter, at the present time most baryons are expected to be in a diffuse
component rather than in stars and galaxies; moreover, ~50 % of this diffuse
component has temperature ~0.01-1 keV and permeates the filamentary
distribution of the dark matter. The temperature of this Warm-Hot Intergalactic
Medium (WHIM) increases with the local density and its search in the outer
regions of clusters and lower density regions has been the quest of much recent
observational effort. Over the last thirty years, an impressive coherent
picture of the formation and evolution of cosmic structures has emerged from
the intense interplay between observations, theory and numerical experiments.
Future efforts will continue to test whether this picture keeps being valid,
needs corrections or suffers dramatic failures in its predictive power.Comment: 20 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 2; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
The CALorimetric Electron Telescope (CALET) for high-energy astroparticle physics on the International Space Station
The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bursts in the 7 keV to 20 MeV energy range during a 5 year mission. These measurements are essential to investigate possible nearby astrophysical sources of high energy electrons, study the details of galactic particle propagation and search for dark matter signatures. The main detector of CALET, the Calorimeter, consists of a module to identify the particle charge, followed by a thin imaging calorimeter (3 radiation lengths) with tungsten plates interleaving scintillating fibre planes, and a thick energy measuring calorimeter (27 radiation lengths) composed of lead tungstate logs. The Calorimeter has the depth, imaging capabilities and energy resolution necessary for excellent separation between hadrons, electrons and gamma rays. The instrument is currently being prepared for launch (expected in 2015) to the International Space Station ISS, for installation on the Japanese Experiment Module - Exposure Facility (JEM-EF)
SLAC T-510 experiment for radio emission from particle showers: Detailed simulation study and interpretation
International audienceOver the last several decades, radio detection of air showers has been widely used to detect ultrahigh-energy cosmic rays. We developed an experiment under controlled laboratory conditions at SLAC with which we measured the radio-frequency radiation from a charged particle shower produced by bunches of electrons as primaries with known energy. The shower took place in a target made of high density polyethylene located in a strong magnetic field. The experiment was designed so that Askaryan and magnetically-induced components of the radio emission could be measured independently. At the same time, we performed a detailed simulation of this experiment to predict the radio signal using two microscopic formalisms, endpoint and ZHS. In this paper, we present the simulation scheme and make a comparison with data characteristics such as linearity with magnetic field and amplitude. The simulations agree with the measurements within uncertainties and present a good description of the data. In particular, reflections within the target that accounted for the largest systematic uncertainties are addressed. The prediction of the amplitude of Askaryan emission agrees with measurements to within 5% for the endpoint formalism and 11% for the ZHS formalism. The amplitudes of magnetically-induced emission agree to within 5% for the endpoint formalism and less than 1% for the ZHS formalism. The agreement of the absolute scale of emission gives confidence in state-of-the-art air shower simulations which are based on the applied formalisms
The design and performance of the XL-Calibur anticoincidence shield
The XL-Calibur balloon-borne hard X-ray polarimetry mission comprises a Compton-scattering polarimeter placed at the focal point of an X-ray mirror. The polarimeter is housed within a BGO anticoincidence shield, which is needed to mitigate the considerable background radiation present at the observation altitude of 40 km. This paper details the design, construction and testing of the anticoincidence shield, as well as the performance measured during the week-long maiden flight from Esrange Space Centre to the Canadian Northwest Territories in July 2022. The in-flight performance of the shield followed design expectations, with a veto threshold 100 keV and a measured background rate of 0.5 Hz (20â40 keV). This is compatible with the scientific goals of the mission, where %-level minimum detectable polarisation is sought for a Hz-level source rate