We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 yr period by ...the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20degrees radius circles. The hotspot has a Li-Ma statistical significance of 5.1sigma, and is centered at R.A. = 146degrees.7, decl. = 43degrees.2. The position of the hotspot is about 19degrees off of the supergalactic plane. The probability of a cluster of events of 5.1sigma significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7 x 10 super(-4) (3.4sigma).
The Telescope Array (TA) observatory utilizes fluorescence detectors and surface detectors (SDs) to observe air showers produced by ultra high energy cosmic rays in Earth's atmosphere. Cosmic-ray ...events observed in this way are termed hybrid data. The depth of air shower maximum is related to the mass of the primary particle that generates the shower. This paper reports on shower maxima data collected over 8.5 yr using the Black Rock Mesa and Long Ridge fluorescence detectors in conjunction with the array of SDs. We compare the means and standard deviations of the observed X max distributions with Monte Carlo X max distributions of unmixed protons, helium, nitrogen, and iron, all generated using the QGSJet II-04 hadronic model. We also perform an unbinned maximum likelihood test of the observed data, which is subjected to variable systematic shifting of the data X max distributions to allow us to test the full distributions, and compare them to the Monte Carlo to see which elements are not compatible with the observed data. For all energy bins, QGSJet II-04 protons are found to be compatible with TA hybrid data at the 95% confidence level after some systematic X max shifting of the data. Three other QGSJet II-04 elements are found to be compatible using the same test procedure in an energy range limited to the highest energies where data statistics are sparse.
EUSO-TA is a cosmic ray detector developed by the JEM-EUSO (Joint Experiment Missions for Extreme Universe Space Observatory) Collaboration, observing during nighttime the fluorescence light emitted ...along the path of extensive air showers in the atmosphere. It is installed at the Telescope Array site in Utah, USA, in front of the fluorescence detector station at Black Rock Mesa. It serves as a ground-based pathfinder experiment for future space-based missions. EUSO-TA has an optical system with two Fresnel lenses and a focal surface with 6 × 6 multi-anode photomultiplier tubes with 64 channels each, for a total of 2304 channels. The overall field of view is ∼10.6°× 10.6°. This detector technology allows the detection of cosmic ray events with high spatial resolution, having each channel a field of view of about ∼0.2° × 0.2° and a temporal resolution of 2.5 µs. First observations of ultra-high energy cosmic rays revealed the cosmic ray detection capability of EUSO-TA. The foreseen upgrade of EUSO-TA will improve the efficiency of the detector and will increase the statistics of detected events. In this work we present recent results of the detection capability of EUSO-TA and its limits. Moreover, other results about the analysis of laser pulses, stars and meteors will be discussed.
We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) ...observatory. The HiRes data are consistent with a constant elongation rate d<X(max)>/dlog(E) of 47.9+/-6.0(stat)+/-3.2(syst) g/cm2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4x10(18) eV.
The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' ...measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.
ABSTRACT We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found ...overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km−2 yr−1 for EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km−2 yr−1 for EeV. This is an order of magnitude lower than previous flux measurements.
We have measured the cosmic ray spectrum at energies above 1017eV using the two air fluorescence detectors of the High Resolution Fly's Eye experiment operating in monocular mode. We describe the ...detector, PMT and atmospheric calibrations, and the analysis techniques for the two detectors. We fit the spectrum to models describing galactic and extragalactic sources. Our measured spectrum gives an observation of a feature known as the “ankle” near 3×1018eV, and strong evidence for a suppression near 6×1019eV.
We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). The TALE air FD is also sensitive to the Cherenkov ...light produced by shower particles. Low-energy cosmic rays, in the PeV energy range, are detectable by TALE as Cherenkov events. Using these events, we measure the energy spectrum from a low energy of ∼2 PeV to an energy greater than 100 PeV. Above 100 PeV, TALE can detect cosmic rays using air fluorescence. This allows for the extension of the measurement to energies greater than a few EeV. In this paper, we describe the detector, explain the technique, and present results from a measurement of the spectrum using ∼1000 hr of observation. The observed spectrum shows a clear steepening near 1017.1 eV, along with an ankle-like structure at 1016.2 eV. These features present important constraints on the origin of galactic cosmic rays and on propagation models. The feature at 1017.1 eV may also mark the end of the galactic cosmic ray flux and the start of the transition to extragalactic sources.
Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but ...utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of Xmax are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.
The surface detector array of the Telescope Array experiment Abu-Zayyad, T.; Aida, R.; Anderson, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2012, Letnik:
689
Journal Article
Recenzirano
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The Telescope Array (TA) experiment, located in the western desert of Utah, USA, is designed for the observation of extensive air showers from extremely high energy cosmic rays. The experiment has a ...surface detector array surrounded by three fluorescence detectors to enable simultaneous detection of shower particles at ground level and fluorescence photons along the shower track. The TA surface detectors and fluorescence detectors started full hybrid observation in March, 2008. In this article we describe the design and technical features of the TA surface detector.
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