284 research outputs found
Coherent Radiation from Extensive Air Showers in the Ultra-High Frequency Band
Using detailed Monte Carlo simulations we have characterized the features of
the radio emission of inclined air showers in the Ultra-High Frequency band
(300 MHz - 3 GHz). The Fourier-spectrum of the radiation is shown to have a
sizable intensity well into the GHz frequency range. The emission is mainly due
to transverse currents induced by the geomagnetic field and to the excess
charge produced by the Askaryan effect. At these frequencies only a
significantly reduced volume of the shower around the axis contributes
coherently to the signal observed on the ground. The size of the coherently
emitting volume depends on frequency, shower geometry and observer position,
and is interpreted in terms of the relative time delays. At ground level, the
maximum emission at high frequencies is concentrated in an elliptical ring-like
region around the intersection of a Cherenkov cone with its vertex at shower
maximum and the ground. The frequency spectrum of inclined showers when
observed at positions that view shower maximum in the Cherenkov direction, is
shown to be in broad agreement with the pulses detected by the Antarctic
Impulsive Transient Antenna (ANITA) experiment, making the interpretation that
they are due to Ultra-High Energy Cosmic Ray atmospheric showers consistent
with our simulations. These results are also of great importance for
experiments aiming to detect molecular bremsstrahlung radiation in the GHz
range as they present an important background for its detection.Comment: 8 pages, 8 figure
Search for microwave emission from ultrahigh energy cosmic rays
We present a search for microwave emission from air showers induced by
ultrahigh energy cosmic rays with the microwave detection of air showers
experiment. No events were found, ruling out a wide range of power flux and
coherence of the putative emission, including those suggested by recent
laboratory measurements.Comment: 5 pages, 3 figure
The Central Laser Facility at the Pierre Auger Observatory
The Central Laser Facility is located near the middle of the Pierre Auger
Observatory in Argentina. It features a UV laser and optics that direct a beam
of calibrated pulsed light into the sky. Light scattered from this beam
produces tracks in the Auger optical detectors which normally record nitrogen
fluorescence tracks from cosmic ray air showers. The Central Laser Facility
provides a "test beam" to investigate properties of the atmosphere and the
fluorescence detectors. The laser can send light via optical fiber
simultaneously to the nearest surface detector tank for hybrid timing analyses.
We describe the facility and show some examples of its many uses.Comment: 4 pages, 5 figures, submitted to 29th ICRC Pune Indi
Studying the nuclear mass composition of Ultra-High Energy Cosmic Rays with the Pierre Auger Observatory
The Fluorescence Detector of the Pierre Auger Observatory measures the
atmospheric depth, , where the longitudinal profile of the high energy
air showers reaches its maximum. This is sensitive to the nuclear mass
composition of the cosmic rays. Due to its hybrid design, the Pierre Auger
Observatory also provides independent experimental observables obtained from
the Surface Detector for the study of the nuclear mass composition. We present
-distributions and an update of the average and RMS values in
different energy bins and compare them to the predictions for different nuclear
masses of the primary particles and hadronic interaction models. We also
present the results of the composition-sensitive parameters derived from the
ground level component.Comment: Proceedings of the 12th International Conference on Topics in
Astroparticle and Underground Physics, TAUP 2011, Munich, German
Hunting long-lived gluinos at the Pierre Auger Observatory
Eventual signals of split sypersymmetry in cosmic ray physics are analyzed in
detail. The study focusses particularly on quasi-stable colorless R-hadrons
originating through confinement of long-lived gluinos (with quarks,
anti-quarks, and gluons) produced in pp collisions at astrophysical sources.
Because of parton density requirements, the gluino has a momentum which is
considerable smaller than the energy of the primary proton, and so production
of heavy (mass ~ 500 GeV) R-hadrons requires powerful cosmic ray engines able
to accelerate particles up to extreme energies, somewhat above 10^{13.6} GeV.
Using a realistic Monte Carlo simulation with the AIRES engine, we study the
main characteristics of the air showers triggered when one of these exotic
hadrons impinges on a stationary nucleon of the Earth atmosphere. We show that
R-hadron air showers present clear differences with respect to those initiated
by standard particles. We use this shower characteristics to construct
observables which may be used to distinguish long-lived gluinos at the Pierre
Auger Observatory.Comment: 13 pages revtex, 9 eps figures. A ps version with high resolution
figures is available at
http://www.hep.physics.neu.edu/staff/doqui/rhadron_highres.p
Las nuevas formas de turismo receptivo en Uruguay. Estudio de caso de las estadĂas por estudios de maestrĂa y doctorado (2005-2010)
O turismo no Uruguai se tornou, na primeira década do século XXI, uma importante atividade econômica
geradora de divisas devido ao aumento do turismo receptor internacional, que escolhe este referido paĂs
do Cone Sul como receptivo. As formas adotadas por este turismo receptor internacional se enquadram
nas tradicionais de sol e mar e turismo termal – turismo recreativo – e também outras formas, dentre
elas, a estada de estudos. Este artigo analisa esta Ăşltima, tomando como foco o caso de estadas de
estudos de pós-graduação – mestrado e doutorado – realizadas por estudantes brasileiros. O enfoque
metodolĂłgico Ă© quantitativo, ao qual foi aplicada uma análise descritiva estatĂstica, acompanhada de
interpretações provenientes da temática do campo teórico do turismo. Estas interpretações apresentaram
como resultado um significativo aumento no receptivo entre os anos de 2005 a 2010, vislumbrando que
seguirão esta tônica, tendo com isso um aumento no gasto médio dos estudantes de pós-graduação
durante suas estadas
The MIDAS experiment: A prototype for the microwave emission of Ultra-High Energy Cosmic Rays
Recent measurements suggest that extensive air showers initiated by
ultra-high energy cosmic rays (UHECR) emit signals in the microwave band of the
electromagnetic spectrum caused by the collisions of the free-electrons with
the atmospheric neutral molecules in the plasma produced by the passage of the
shower. Such emission is isotropic and could allow the detection of air showers
with 100% duty cycle and a calorimetric-like energy measurement, a significant
improvement over current detection techniques. We have built MIDAS (MIcrowave
Detection of Air Showers), a prototype of microwave detector, which consists of
a 4.5 m diameter antenna with a cluster of 53 feed-horns in the 4 GHz range.
The details of the prototype and first results will be presented.Comment: To appear in the proceedings of 12th Topical Seminar on Innovative
Particle and Radiation Detectors (IPRD10), Siena, Italy, 7 - 10 June 201
The Air Microwave Yield (AMY) experiment - A laboratory measurement of the microwave emission from extensive air showers
The AMY experiment aims to measure the microwave bremsstrahlung radiation
(MBR) emitted by air-showers secondary electrons accelerating in collisions
with neutral molecules of the atmosphere. The measurements are performed using
a beam of 510 MeV electrons at the Beam Test Facility (BTF) of Frascati INFN
National Laboratories. The goal of the AMY experiment is to measure in
laboratory conditions the yield and the spectrum of the GHz emission in the
frequency range between 1 and 20 GHz. The final purpose is to characterise the
process to be used in a next generation detectors of ultra-high energy cosmic
rays. A description of the experimental setup and the first results are
presented.Comment: 3 pages -- EPS-HEP'13 European Physical Society Conference on High
Energy Physics (July, 18-24, 2013) at Stockholm, Swede
- …