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71.
On-orbit performance of the top and bottom counting detectors for the ISS-CREAM experiment on the international space station
J. P. Lundquist, S.C. Kang, 2019, izvirni znanstveni članek

Opis: The Cosmic Ray Energetics And Mass (CREAM) instrument on the International Space Station (ISS) is an experiment to study origin, propagation, acceleration and elemental composition of cosmic rays. The Top Counting Detector (TCD) and Bottom Counting Detector (BCD) are parts of the detector suite of the ISS-CREAM experiment and are designed to separate electrons and protons for studying electron and gamma-ray physics. In addition, the TCD/BCD provide a redundant trigger to that of the calorimeter and a low energy trigger to the ISS-CREAM instrument. After launching, the TCD/BCD trigger was found to be working well. Also, the TCD/BCD have been stable and their hit positions were confirmed to be well matched with other detectors on board. We present the performance and status of the TCD/BCD in flight.
Najdeno v: ključnih besedah
Povzetek najdenega: ...The Cosmic Ray Energetics And Mass (CREAM) instrument on...
Ključne besede: ISS-CREAM, CREAM, Cosmic rays, TCD/BCD
Objavljeno: 27.04.2020; Ogledov: 433; Prenosov: 19
.pdf Polno besedilo (2,00 MB)

72.
Full-sky searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope Array
J. P. Lundquist, A. di Matteo, 2020, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, Cosmic Rays, Anisotropy...
Ključne besede: UHECR, Cosmic Rays, Anisotropy
Objavljeno: 27.04.2020; Ogledov: 398; Prenosov: 0
.pdf Polno besedilo (6,28 MB)

73.
Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data
J. P. Lundquist, R.U. Abbasi, 2019, izvirni znanstveni članek

Opis: The results on ultrahigh-energy cosmic rays (UHECR) mass composition obtained with the Telescope Array surface detector are presented. The analysis employs the Boosted Decision tree (BDT) multivariate analysis built upon 14 observables related to both the properties of the shower front and the lateral distribution function. The multivariate classifier is trained with Monte-Carlo sets of events induced by the primary protons and iron. An average atomic mass of UHECR is presented for energies 10^18.0–10^20.0 eV. The average atomic mass of primary particles shows no significant energy dependence and corresponds to ⟨lnA⟩=2.0±0.1 (stat.)±0.44(syst.). The result is compared to the mass composition obtained by the Telescope Array with Xmax technique along with the results of other experiments. Possible systematic errors of the method are discussed.
Najdeno v: ključnih besedah
Ključne besede: UHECR, Cosmic rays, composition
Objavljeno: 27.04.2020; Ogledov: 457; Prenosov: 0
.pdf Polno besedilo (10,07 MB)

74.
Testing a Reported Correlation between Arrival Directions of Ultra-high-energy Cosmic Rays and a Flux Pattern from nearby Starburst Galaxies using Telescope Array Data
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did not optimize the parameter values but kept them fixed to the best-fit values found by Auger, namely 9.7% for the anisotropic fraction of cosmic rays assumed to originate from the SBGs in the list and 12.9◦ for the angular scale of the correlations. The energy threshold we adopted is 43 EeV, corresponding to 39 EeV in Auger when taking into account the energy-scale difference between two experiments. We find that the TA data is compatible with isotropy to within 1.1σ and with the Auger result to within 1.4σ, meaning that it is not capable to discriminate between these two hypotheses.
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, cosmic rays, galaxies: starburst, methods: data analysis
Objavljeno: 27.04.2020; Ogledov: 496; Prenosov: 30
.pdf Polno besedilo (700,72 KB)

75.
Evidence for Declination Dependence of Ultrahigh Energy Cosmic Ray Spectrum in the Northern Hemisphere
J. P. Lundquist, R.U. Abbasi, 2018, drugi članki ali sestavki

Opis: The energy of the ultrahigh energy spectral cutoff was measured, integrating over the northern hemisphere sky, by the Telescope Array (TA) collaboration, to be 10^19.78±0.06 eV, in agreement with the High Resolution Fly's Eye (HiRes) experiment, whereas the Pierre Auger experiment, integrating over the southern hemisphere sky, measured the cutoff to be at 10^19.62±0.02 eV. An 11% energy scale difference between the TA and Auger does not account for this difference. However, in comparing the spectra of the Telescope Array and Pierre Auger experiments in the band of declination common to both experiments ( −15.7∘<δ<24.8∘ ) we have found agreement in the energy of the spectral cutoff. While the Auger result is essentially unchanged, the TA cutoff energy has changed to 10^19.59±0.06 eV. In this paper we argue that this is an astrophysical effect.
Najdeno v: ključnih besedah
Ključne besede: Astrophysics, High Energy Astrophysical Phenomena, UHECR, Cosmic Rays, Anisotropy, Energy Spectrum
Objavljeno: 27.04.2020; Ogledov: 508; Prenosov: 21
.pdf Polno besedilo (687,87 KB)

76.
Depth of Ultra High Energy Cosmic Ray Induced Air Shower Maxima Measured by the Telescope Array Black Rock and Long Ridge FADC Fluorescence Detectors and Surface Array in Hybrid Mode
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: 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 Xmax distributions with Monte Carlo Xmax 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 Xmax 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 Xmax 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.
Najdeno v: ključnih besedah
Ključne besede: acceleration of particles, astrochemistry, astroparticle physics, cosmic rays, elementary particles, UHECR, composition
Objavljeno: 27.04.2020; Ogledov: 480; Prenosov: 0
.pdf Polno besedilo (5,52 MB)

77.
Search for Anisotropy in the Ultra High Energy Cosmic Ray Spectrum using the Telescope Array Surface Detector
J. P. Lundquist, R.U. Abbasi, 2017, drugi članki ali sestavki

Opis: The Telescope Array (TA) experiment is located in the western desert of Utah, USA, and observes ultra high energy cosmic rays (UHECRs) in the Northern hemisphere. At the highest energies, E>10~EeV, the shape of cosmic ray energy spectrum may carry an imprint of the source density distribution along the line of sight different in different directions of the sky. In this study, we search for such directional variations in the shape of the energy spectrum using events observed with the Telescope Array's surface detector. We divide the TA field of view into two nearly equal-exposure regions: the "on-source" region which we define as ±30∘ of the supergalactic plane containing mostly nearby structures, and the complementary "off-source" region where the sources are further away on average. We compare the UHECR spectra in these regions by fitting them to the broken power law and comparing the resulting parameters. We find that the off-source spectrum has an earlier break at highest energies. The chance probability to obtain such or larger difference in statistically equivalent distributions is estimated as 6.2±1.1×10−4 (3.2σ) by a Monte-Carlo simulation. The observed difference in spectra is in a reasonable quantitative agreement with a simplified model that assumes that the UHECR sources trace the galaxy distribution from the 2MRS catalogue, primary particles are protons and the magnetic deflections can be neglected.
Najdeno v: ključnih besedah
Ključne besede: cosmic radiation: UHE, detector: surface, cosmic radiation: spectrum, cosmic radiation: energy spectrum, deflection: magnetic, numerical calculations: Monte Carlo, anisotropy
Objavljeno: 27.04.2020; Ogledov: 442; Prenosov: 21
.pdf Polno besedilo (169,05 KB)

78.
The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven years
J. P. Lundquist, R.U. Abbasi, 2016, izvirni znanstveni članek

Opis: 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 10^17.2eV measured by the fluorescence detectors and a comparison with previously published results.
Najdeno v: ključnih besedah
Ključne besede: Cosmic rays, Ultra-high energy, Fluorescence detector, Energy spectrum, Ankle, GZK cutoff
Objavljeno: 27.04.2020; Ogledov: 443; Prenosov: 0
.pdf Polno besedilo (1,23 MB)

79.
First upper limits on the radar cross section of cosmic-ray induced extensive air showers
J. P. Lundquist, R.U. Abbasi, 2017, izvirni znanstveni članek

Opis: 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 (∼ 10 µs) and exhibit rapidly changing frequency, with rates on the order 1 MHz/µs. 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.
Najdeno v: ključnih besedah
Ključne besede: Cosmic ray, Radar, Digital signal processing, Radar cross-section
Objavljeno: 27.04.2020; Ogledov: 412; Prenosov: 0
.pdf Polno besedilo (6,16 MB)

80.
Measurement of the proton-air cross section with Telescope Array’s Middle Drum detector and surface array in hybrid mode
J. P. Lundquist, R.U. Abbasi, 2015, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ... Cosmic Rays, proton cross-section, ultra-high energy, particle physics...
Ključne besede: Cosmic Rays, proton cross-section, ultra-high energy, particle physics
Objavljeno: 27.04.2020; Ogledov: 436; Prenosov: 0
.pdf Polno besedilo (409,81 KB)

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