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Raman LIDARs and atmospheric calibration along the line-of-sight of the Cherenkov Telescope Array
Samo Stanič, Longlong Wang, Marko Zavrtanik, 2019, objavljeni znanstveni prispevek na konferenci

Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies. Employing more than 100 (north and south sites) Imaging Atmospheric Cherenkov Telescopes in the northern and southern hemispheres, it was designed to reach unprecedented sensitivity and energy resolution. Understanding and correcting for systematic biases on the absolute energy scale and instrument response functions will be a cru- cial issue for the performance of CTA. The Montpellier group and the Spanish/Italian/Slovenian collaboration are currently building two Raman LIDAR prototypes for the online atmospheric cal- ibration along the line-of-sight of the CTA. Requirements for such a solution include the ability to characterize aerosol extinction at two wavelengths to distances up to 30 km with an accuracy better than 5%, within exposure time scales of about a minute, steering capabilities and close interaction with the CTA array control and data acquisition system as well as other auxiliary in- struments. Our Raman LIDARs have design features that make them different from those used in atmospheric science and are characterized by large collecting mirrors (∼2.5 m 2 ), liquid light- guides that collect the light at the focal plane and transport it to the readout system, reduced acquisition time and highly precise Raman spectrometers. The Raman LIDARs will participate in a cross-calibration and characterization campaign of the atmosphere at the CTA North site at La Palma, together with other site characterization instruments. After a one-year test period there, an in-depth evaluation of the solutions adopted by the two projects will lead to a final Raman LIDAR design proposal for both CTA sites.
Najdeno v: ključnih besedah
Ključne besede: Raman lidar atmospheric calibration Cherenkov Telescope Array
Objavljeno: 29.08.2019; Ogledov: 2173; Prenosov: 72
.pdf Polno besedilo (1,29 MB)

125.
Study of Ultra-High Energy Cosmic Ray composition using Telescope Array’s Middle Drum detector and surface array in hybrid mode
Jon Paul Lundquist, R.U. Abbasi, 2015, izvirni znanstveni članek

Opis: 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 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.
Najdeno v: ključnih besedah
Ključne besede: Ultra-High Energy Cosmic Rays, Cosmic ray composition, Atmospheric fluorescence, Extensive air shower array, Hybrid, Telescope Array
Objavljeno: 24.04.2020; Ogledov: 1775; Prenosov: 0
.pdf Polno besedilo (3,45 MB)

126.
The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface array
J. P. Lundquist, R.U. Abbasi, 2015, izvirni znanstveni članek

Opis: 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.
Najdeno v: ključnih besedah
Ključne besede: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energy
Objavljeno: 27.04.2020; Ogledov: 1553; Prenosov: 0
.pdf Polno besedilo (3,12 MB)

127.
Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeV
J. P. Lundquist, R.U. Abbasi, 2010, izvirni znanstveni članek

Opis: We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (Xmax), 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⟨Xmax⟩/d[log(E)] of 47.9 ± 6.0 (stat) ± 3.2 (syst) g/cm^2/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 4×10^18 eV.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energy...
Ključne besede: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energy
Objavljeno: 27.04.2020; Ogledov: 1584; Prenosov: 0
.pdf Polno besedilo (314,89 KB)

128.
TA Anisotropy Summary
J. P. Lundquist, K. Kawata, 2019, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array (TA) is the largest ultra-high-energy cosmic-ray (UHECR) detector in the northern hemisphere. It consists of an array of 507 surface detectors (SD) covering a total 700 km^2 and three fluorescence detector stations overlooking the SD array. In this proceedings, we summarize recent results on the search for directional anisotropy of UHECRs using the latest dataset collected by the TA SD array. We obtained hints of the anisotropy of the UHECRs in the northern sky from the various analyses.
Najdeno v: ključnih besedah
Povzetek najdenega: ...The Telescope Array (TA) is the largest ultra-high-energy cosmic-ray...
Ključne besede: cosmic radiation, UHE detector, fluorescence detector, surface, Telescope Array Experiment, anisotropy, experimental results
Objavljeno: 28.04.2020; Ogledov: 1633; Prenosov: 54
.pdf Polno besedilo (1,88 MB)

129.
Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression
J. P. Lundquist, J. Biteau, 2019, objavljeni znanstveni prispevek na konferenci

Opis: Despite deflections by Galactic and extragalactic magnetic fields, the distribution of ultra-high energy cosmic rays (UHECRs) over the celestial sphere remains a most promising observable for the identification of their sources. Thanks to a large number of detected events over the past years, a large-scale anisotropy at energies above 8 EeV has been identified, and there are also indications from the Telescope Array and Pierre Auger Collaborations of deviations from isotropy at intermediate angular scales (about 20 degrees) at the highest energies. In this contribution, we map the flux of UHECRs over the full sky at energies beyond each of two major features in the UHECR spectrum – the ankle and the flux suppression, and we derive limits for anisotropy on different angular scales in the two energy regimes. In particular, full-sky coverage enables constraints on low-order multipole moments without assumptions about the strength of higher-order multipoles. Following previous efforts from the two Collaborations, we build full-sky maps accounting for the relative exposure of the arrays and differences in the energy normalizations. The procedure relies on cross-calibrating the UHECR fluxes reconstructed in the declination band around the celestial equator covered by both observatories. We present full-sky maps at energies above ~10 EeV and ~50 EeV, using the largest datasets shared across UHECR collaborations to date. We report on anisotropy searches exploiting full-sky coverage and discuss possible constraints on the distribution of UHECR sources.
Najdeno v: ključnih besedah
Povzetek najdenega: ...and there are also indications from the Telescope Array and Pierre Auger Collaborations of deviations...
Ključne besede: UHECR, cosmic rays, anisotropy, Telescope Array, Pierre Auger Observatory
Objavljeno: 28.04.2020; Ogledov: 1485; Prenosov: 55
.pdf Polno besedilo (4,92 MB)

130.
Constraints on the diffuse photon flux with energies above 10^18 eV using the surface detector of the Telescope Array experiment
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: We present the results of the search for ultra-high-energy photons with nine years of data from the Telescope Array surface detector. A multivariate classifier is built upon 16 reconstructed parameters of the extensive air shower. These parameters are related to the curvature and the width of the shower front, the steepness of the lateral distribution function, and the timing parameters of the waveforms sensitive to the shower muon content. A total number of two photon candidates found in the search is fully compatible with the expected background. The 95% CL limits on the diffuse flux of the photons with energies greater than 10^18.0, 10^18.5, 10^19.0, 10^19.5 and 10^20.0 eV are set at the level of 0.067, 0.012, 0.0036, 0.0013, correspondingly.
Najdeno v: ključnih besedah
Ključne besede: Ultra-high-energy photons, Telescope array experiment, Extensive air showers
Objavljeno: 30.04.2020; Ogledov: 1671; Prenosov: 0
.pdf Polno besedilo (1,33 MB)

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