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Search for EeV protons of galactic origin
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Fujii, T.,Fukushima, M.,Goto, T.,Hanlon, W.,Haya North-Holland 2017 Astroparticle physics Vol.86 No.-
<P>Cosmic rays in the energy range 10(18.0)-10(18.5) eV are thought to have a light, probably protonic, composition. To study their origin one can search for anisotropy in their arrival directions. Extragalactic cosmic rays should be isotropic, but galactic cosmic rays of this type should be seen mostly along the galactic plane, and there should be a shortage of events coming from directions near the galactic anticenter. This is due to the fact that, under the influence of the galactic magnetic field, the transition from ballistic to diffusive behavior is well advanced, and this qualitative picture persists over the whole energy range. Guided by models of the galactic magnetic field that indicate that the enhancement along the galactic plane should have a standard deviation of about 20 degrees in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50 degrees in galactic longitude, we use the data of the Telescope Array surface detector in 10(18.0) to 10(18.5) eV energy range to search for these effects. The data are isotropic. Neither an enhancement along the galactic plane nor a deficit in the galactic anticenter direction is found. Using these data we place an upper limit on the fraction of EeV cosmic rays of galactic origin at 1.3% at 95% confidence level. Published by Elsevier B.V.</P>
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fukushima, M.,Goto, T.,Hanlo North-Holland 2016 Astroparticle physics Vol.80 No.-
<P>The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at two stations of TA are newly constructed and have now completed seven years of steady operation. One advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. Analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 10(17.2)eV measured by the fluorescence detectors and a comparison with previously published results. (C) 2016 Elsevier B.V. All rights reserved.</P>
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fuku Elsevier 2015 Astroparticle physics Vol.64 No.-
<P><B>Abstract</B></P> <P>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 <SUB> X max </SUB> 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.</P>
The hybrid energy spectrum of Telescope Array's Middle Drum Detector and surface array
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.G.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fu North-Holland ; Elsevier Science Ltd 2015 Astroparticle physics Vol.68 No.-
The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly's Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.
Abbasi, R. U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Chae, M. J.,Cheon, B. G.,Chiba, J.,Chikawa, M.,Cho, W. R.,Fujii, IOP Publishing 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.790 No.2
<P>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 20 degrees radius circles. The hotspot has a Li-Ma statistical significance of 5.1 sigma, and is centered at R. A. = 146 degrees 7, decl. = 43 degrees 2. The position of the hotspot is about 19 degrees off of the supergalactic plane. The probability of a cluster of events of 5.1 sigma significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7 x 10(-4) (3.4 sigma).</P>
Abbasi, R. U.,Abe, M.,Zayyad, T. Abu-,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Chae, M. J.,Cheon, B. G.,Chiba, J.,Chikawa, M.,Cho, W. R.,Fujii, IOP Publishing 2015 The Astrophysical journal Vol.804 No.2
<P>We report on the search for steady point-like sources of neutral particles around 10(18) 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 E > 1 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 E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.</P>
First upper limits on the radar cross section of cosmic-ray induced extensive air showers
Abbasi, R.U.,Abe, M.,Abou Bakr Othman, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Besson, D.,Blake, S.A.,Byrne, M.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chib North-Holland 2017 Astroparticle physics Vol.87 No.-
<P>TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data since 2013 with the primary goal of observing the radar signatures of extensive air showers (EAS). Simulations indicate that echoes are expected to be short in duration (similar to 10 mu s) and exhibit rapidly changing frequency, with rates on the order 1 MHz/mu s. The EAS radar cross-section (RCS) is currently unknown although it is the subject of over 70 years of speculation. A novel signal search technique is described in which the expected radar echo of a particular air shower is used as a matched filter template and compared to waveforms obtained by triggering the radar DAQ using the Telescope Array fluorescence detector. No evidence for the scattering of radio frequency radiation by EAS is obtained to date. We report the first quantitative RCS upper limits using EAS that triggered the Telescope Array Fluorescence Detector. (C) 2016 Elsevier B.V. All rights reserved.</P>
EBSD and reconstruction of pre-transformation microstructures, examples and complexities in steels
Abbasi, M.,Kim, D.I.,Nelson, T.W.,Abbasi, M. Elsevier 2014 Materials characterization Vol.95 No.-
Electron backscattered diffraction has provided a quantitative tool to study micro/nano-structures in large scales. A recent application of electron backscattered diffraction is the reconstruction of pre-transformed phases in polymorphic systems, especially when there is no retained pre-transformed phase at room temperature. This capability has been demonstrated by various researchers utilizing different approaches towards grain structure and orientation recovery. However, parameters affecting reconstruction have not been investigated systematically. Factors such as post-transformed microstructures (morphology and crystallography), lattice strain (deformation), pattern and sample quality are among the affecting factors. Two-dimensional datasets of different steels have been reconstructed along with a limited 3-dimensional dataset in the current paper. Preliminary results intended for large-scale automatic reconstructions have been presented. They indicate that the successfulness of reconstruction is strongly dependent on the post-transformed microstructure. Factors such as morphology, grain size, variant selection, and deformation play roles. Few examples of reconstruction complexity at prior austenite boundaries leading to uncertain results are presented. Lastly, reconstructions are discussed in terms of meaningfulness and if they correctly represent pre-transformed grains and orientations.
Lattice Boltzmann simulation of condensation over different cross sections and tube banks
M. Abbasi Hatani,H. Amirshaghaghi,M. H. Rahimian,A. Begmohammadi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10
In this paper a two-phase Lattice Boltzmann model, capable of handling large density jumps, is used to simulate the vapor filmwise condensation and dew drop sprinkling, outside different horizontal geometries. These geometries include circle, rectangle, square, and a bank of circular and rectangular tubes. In order to calculate the temperature field a passive scalar approach is combined with the Lattice Boltzmann framework and the flow field is assumed to be affected by temperature under the hypothesis of Boussinesq. Additionally, the effect of phase-change on velocity field is taken into account by adding a suitable source term to the pressure-momentum distribution equation. To simplify the model, it is assumed that the vapor remains at the saturation temperature and the amount of heat transferred through the interface is the only driving force for condensation. To demonstrate the validity of the model, the results are compared with a variety of analytical, numerical and experimental data. The validated model then is employed to study the influence of different parameters such as vapor temperature, Stefan number and Archimedes number on vapor condensation outside multiple cross sections. Finally, the condensate inundation and mean heat transfer coefficients are analyzed in horizontal tube banks.
Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data
Abbasi, R. U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Cheon, B. G.,Chiba, J.,Chikawa, M.,di Matteo, A.,Fujii, T.,Fujita, K.,Fukushim American Physical Society 2019 Physical review. D Vol.99 No.2