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91.
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
Ključne besede: UHECR, cosmic rays, anisotropy, Telescope Array, Pierre Auger Observatory
Objavljeno: 28.04.2020; Ogledov: 390; Prenosov: 18
.pdf Polno besedilo (4,92 MB)

92.
Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E>10^19.2 eV with the Telescope Array Surface Detector
J. P. Lundquist, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Evidence of an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays of energies above 10^19.2 eV in the northern hemisphere, using 7 years of Telescope Array (TA) surface detector (SD) data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 139 R.A., 45 Dec., and has a deficit of events with energies 10^19.210^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo (MC) simulation to be 9x10^-5 (3.74 σ_global).
Najdeno v: ključnih besedah
Ključne besede: UHECR, cosmic rays, energy spectrum, anisotropy
Objavljeno: 29.04.2020; Ogledov: 394; Prenosov: 20
.pdf Polno besedilo (408,40 KB)

93.
Telescope Array Composition Summary
J. P. Lundquist, W. Hanlon, 2018, objavljeni znanstveni prispevek na konferenci

Opis: Ultra high energy cosmic ray (UHECR) chemical composition is important to resolving questions about the locations of UHECR sources and propagation models. Because composition can only be deduced by a process of statistical inference via the observation of air shower maxima (Xmax), UHECR observatories with large data collection rates must be employed to reduce statistical fluctuations. Telescope Array (TA), the largest cosmic ray observatory in the Northern Hemisphere, is designed to answer the question of UHECR composition, as well as other important features of cosmic ray flux, by combining a large array of over 500 scintillation surface detectors spread over 700 km^2, and three fluorescence detector stations overlooking the array. With eight years of data recorded, results of the measurements of UHECR composition will be presented. UHECR composition is traditionally measured by comparing the first and second moments of the distributions of shower maxima, which evolves with energy, between data and simulations. Reducing statistical fluctuations in the data helps to distinguish between different primary elements in the flux. In the current generation of cosmic ray observatories, UHECR data sets are large enough, and statistical uncertainties are now small enough, that we can safely distinguish between very light primary source flux (i.e., protons) and heavy flux (i.e., iron). Reducing systematic uncertainties is also important though, since large systematic shifts in air shower maxima will influence the interpretation of the data when compared to models. TA therefore employs different methods of measuring Xmax, including stereo air fluorescence, air fluorescence-surface counter hybrid, and a new technique using only surface counters. Updated results of TA hybrid composition among the different methods are presented using up to eight years of data. Agreement among all TA hybrid composition results are shown as well as detailed systematic errors which can be further explored by comparing composition results of the different measurement methods. Comparison of TA Xmax data are compared to different composition models as well.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Ultra high energy cosmic ray (UHECR) chemical composition is important to resolving...
Ključne besede: UHECR, Cosmic rays, composition
Objavljeno: 29.04.2020; Ogledov: 375; Prenosov: 19
.pdf Polno besedilo (499,33 KB)

94.
Telescope Array anisotropy summary
J. P. Lundquist, M. Fukushima, 2018, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array has accumulated the largest UHECR data set in the Northern hemisphere. We make use of these data to search for large- and small-scale anisotropy of UHECR arrival directions. At small angular scales, we report an update on searches for clustering of events and on correlations with various classes of putative sources. At large angular scales, we revisit, with the new data and with new tests, the localized excess of events known as the TA “hot spot”. We review some other studies of the arrival directions and corresponding implications for the nature of UHECR sources.
Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, cosmic rays, anisotropy...
Ključne besede: UHECR, cosmic rays, anisotropy
Objavljeno: 29.04.2020; Ogledov: 374; Prenosov: 19
.pdf Polno besedilo (581,87 KB)

95.
A systematic uncertainty on the energy scale of the Telescope Array fluorescence detectors
J. P. Lundquist, T. Fujii, 2018, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array experiment (TA) is the largest cosmic-ray detector in the northern hemi-sphere and consists of a surface detector (SD) array, plus three fluorescence detector (FD) stations overlooking the SD. The large field-of-view of an FD allows for reconstruction of the air-shower development in the atmosphere by imaging ultra-violet fluorescence light from atmospheric nitrogen excited by UHECRs. In estimation of the primary energy it is necessary to add to the calorimetric energy observed by the FD a “missing energy”, meaning the fraction of the primary energy that is not deposited by charged particles in the air. We report on the measurement of the missing energy from observed data collected by the TA FD and TA SD, independently of Monte Carlo simulations, using a technique pioneered by the Pierre Auger Observatory. We also address the effect on the energy scale attributed to fluorescence yield parameters.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Telescope Array experiment (TA) is the largest cosmic-ray detector in the northern hemi-sphere and consists...
Ključne besede: UHECR, cosmic rays, energy spectrum
Objavljeno: 29.04.2020; Ogledov: 366; Prenosov: 18
.pdf Polno besedilo (4,74 MB)

96.
Composition Measurements via Depth of Airshower Maximum at the Telescope Array
W. Hanlon, J. P. Lundquist, 2018, objavljeni znanstveni prispevek na konferenci

Opis: Telescope Array (TA) was designed to answer important questions about the UHECR flux with energies above 10^17 eV such as spectrum, arrival direction, and mass composition. Because the UHECR flux is rapidly falling in this energy region, TA’s large exposure makes it one of the few experiments in the world that can adequately explore these issues. Composition is particularly difficult to measure because mass can not be measured directly due to the low flux. TA’s multiple methods of observing UHECR induced air showers will be explained, as well as how composition can be measured by these methods. Good agreement among the different measurement techniques is found leading to greater confidence in measuring UHECR mass composition and a way to test and understand TA systematic uncertainties.
Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, cosmic rays, composition...
Ključne besede: UHECR, cosmic rays, composition
Objavljeno: 29.04.2020; Ogledov: 369; Prenosov: 21
.pdf Polno besedilo (758,27 KB)

97.
The Nature and Origin of Ultra-high Energy Cosmic Ray Particles
J. P. Lundquist, P.L. Biermann, 2016, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje)

Opis: We outline two concepts to explain Ultra High Energy Cosmic Rays (UHECRs), one based on radio galaxies and their relativistic jets and terminal hot spots, and one based on relativistic Super-Novae (SNe) or Gamma Ray Bursts (GRBs) in starburst galaxies, one matching the arrival direction data in the South (the radio galaxy Cen A) and one in the North (the starburst galaxy M82). The most likely identification of the origin of observed Gravitational Wave (GW) events is stellar binary black hole (BH) mergers in starburst galaxies such as M82 with the highest rate of star formation, so the highest far-infrared (FIR) luminosity, at the edge of the universe visible in 10 - 300 Hz GWs; at low heavy element abundance Zch the formation of stellar BHs extends to a larger mass range. A radio galaxy such as Cen A sequence of events involves first the merger of two Super-Massive Black Holes (SMBHs), with the associated ejection of low frequency GWs, then the formation of a new relativistic jet aiming into a new direction: ubiquitous neutrino emission follows accompanied by compact TeV photon emission, detectable more easily if the direction is towards Earth. The ejection of UHECRs is last. Both these sites are the perfect high energy physics laboratory: We have observed particles up to ZeV, neutrinos up to PeV, photons up to TeV, 30 - 300 Hz GW events, and hope to detect soon of order µHz to mHz GW events. Energy turnover in single low frequency GW events may be of order ∼1063 erg. How can we further test these concepts? First of all by associating individual UHECR events, or directional groups of events, with chemical composition in both the Telescope Array (TA) Coll. and the Auger Coll. data. Second by identifying more TeV to PeV neutrinos with recent SMBH mergers. Third by detecting the order < mHz GW events of SMBH binaries, and identifying the galaxies host to the stellar BH mergers and their GW events in the range up to 300 Hz. Fourth by finally detecting the formation of the first generation of SMBHs and their mergers, surely a spectacular discovery.
Najdeno v: ključnih besedah
Ključne besede: UHECR, cosmic rays, anisotropy
Objavljeno: 29.04.2020; Ogledov: 342; Prenosov: 18
.pdf Polno besedilo (372,72 KB)

98.
Cosmic Ray Shower Profile Track Finding for Telescope Array Fluorescence Detectors
J. P. Lundquist, 2016, objavljeni znanstveni prispevek na konferenci

Opis: A simple cosmic ray track finding pattern recognition analysis (PRA) method for fluorescence detectors (FD) has been developed which significantly improves Xmax resolution and its dependence on energy. Events which have a clear rise and fall in the FD view contain information on Xmax that can be reliably reconstructed. Shower maximum must be extrapolated for events with Xmax outside the field of view of the detector, which creates a systematic dependence on the fitting function. The PRA method is a model and detector independent approach to removing these events, by fitting shower profiles to a set of triangles and applying limits on the allowable geometry.
Najdeno v: ključnih besedah
Ključne besede: UHECR, cosmic rays, fluorescence detector, track finding, pattern recognition
Objavljeno: 29.04.2020; Ogledov: 431; Prenosov: 38
.pdf Polno besedilo (1,59 MB)

99.
Study of UHECR Composition Using Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode
J. P. Lundquist, 2016, objavljeni znanstveni prispevek na konferenci

Opis: The seven year Telescope Array (TA) Middle Drum hybrid composition measurement shows agreement between Ultra-High Energy Cosmic Ray (UHECR) data and a light composition obtained with QGSJetII-03 or QGSJet-01c models. The data are incompatible with a pure iron composition, for all models examined, for energies log10(E/eV)>18.4. This is consistent with previous TA results. This analysis is presented using an updated version of the pattern recognition analysis (PRA) technique developed by TA.
Najdeno v: ključnih besedah
Povzetek najdenega: ...composition measurement shows agreement between Ultra-High Energy Cosmic Ray (UHECR) data and a light composition...
Ključne besede: UHECR, cosmic rays, hybrid detection, composition
Objavljeno: 29.04.2020; Ogledov: 395; Prenosov: 19
.pdf Polno besedilo (150,19 KB)

100.
Report of the Working Group on the Composition of Ultra-High Energy Cosmic Rays
J. P. Lundquist, M. Unger, 2016, objavljeni znanstveni prispevek na konferenci

Opis: The atmospheric depth, Xmax, at which the particle number of an air shower reaches its maximum is a good indicator for the mass of the primary particle. We present a comparison of the energy evolution of the mean of Xmax as measured by the Telescope Array and Pierre Auger Collaborations. After accounting for the different resolutions, acceptances and analysis strategies of the two experiments, the two results are found to be in good agreement within systematic uncertainties.
Najdeno v: ključnih besedah
Ključne besede: UHECR, cosmic rays, composition
Objavljeno: 29.04.2020; Ogledov: 460; Prenosov: 19
.pdf Polno besedilo (329,86 KB)

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