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21.
Study of muons from ultrahigh energy cosmic ray air showers measured with the Telescope Array experiment
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: One of the uncertainties in the interpretation of ultrahigh energy cosmic ray data comes from the hadronic interaction models used for air shower Monte Carlo (MC) simulations. The number of muons observed at the ground from ultrahigh energy cosmic ray–induced air showers is expected to depend upon the hadronic interaction model. One may therefore test the hadronic interaction models by comparing the measured number of muons with the MC prediction. In this paper, we present the results of studies of muon densities in ultrahigh energy extensive air showers obtained by analyzing the signal of surface detector stations which should have high muon purity. The muon purity of a station will depend on both the inclination of the shower and the relative position of the station. In seven years’ data from the Telescope Array experiment, we find that the number of particles observed for signals with an expected muon purity of ∼65% at a lateral distance of 2000 m from the shower core is 1.72± 0.10(stat)±0.37(syst) times larger than the MC prediction value using the QGSJET II-03 model for proton-induced showers. A similar effect is also seen in comparisons with other hadronic models such as QGSJET II-04, which shows a 1.67±0.10±0.36 excess. We also studied the dependence of these excesses on lateral distances and found a slower decrease of the lateral distribution of muons in the data as compared to the MC, causing larger discrepancy at larger lateral distances.
Najdeno v: osebi
Ključne besede: UHECR, cosmic rays, muons, particle physics
Objavljeno: 30.04.2020; Ogledov: 1012; Prenosov: 0
.pdf Polno besedilo (2,16 MB)

22.
The bursts of high energy events observed by the telescope array surface detector
J. P. Lundquist, R.U. Abbasi, 2017, izvirni znanstveni članek

Opis: The Telescope Array (TA) experiment is designed to detect air showers induced by ultra high energy cosmic rays. The TA ground Surface particle Detector (TASD) observed several short-time bursts of air shower like events. These bursts are not likely due to chance coincidence between single shower events. The expectation of chance coincidence is less than 10^-4 for five-year's observation. We checked the correlation between these bursts of events and lightning data, and found evidence for correlations in timing and position. Some features of the burst events are similar to those of a normal cosmic ray air shower, and some are not. On this paper, we report the observed bursts of air shower like events and their correlation with lightning.
Najdeno v: osebi
Ključne besede: High energy radiation, Lightning, Terrestrial gamma-ray flash
Objavljeno: 30.04.2020; Ogledov: 1127; Prenosov: 0
.pdf Polno besedilo (1,70 MB)

23.
Search for EeV protons of galactic origin
J. P. Lundquist, R.U. Abbasi, 2016, izvirni znanstveni članek

Opis: 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° in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50° 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.
Najdeno v: osebi
Ključne besede: Cosmic ray, Galactic protons, Telescope array, Surface detector
Objavljeno: 30.04.2020; Ogledov: 1107; Prenosov: 0
.pdf Polno besedilo (840,97 KB)

24.
Search for ultra-high-energy neutrinos with the Telescope Array surface detector
Mitsuhiro Abe, R. U. Abbasi, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: We present an upper limit on the flux of ultra-high-energy down-going neutrinos for E > 10^18 eV derived with the nine years of data collected by the Telescope Array surface detector (05-11-2008– 05-10-2017). The method is based on the multivariate analysis technique, so-called Boosted Decision Trees (BDT). Proton-neutrino classifier is built upon 16 observables related to both the properties of the shower front and the lateral distribution function.
Najdeno v: osebi
Ključne besede: neutrinos, pattern recognition, UHECR, cosmic rays
Objavljeno: 29.04.2020; Ogledov: 1101; Prenosov: 40
URL Polno besedilo (0,00 KB)
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25.
Measurement of the proton-air cross section with Telescope Array's Black Rock Mesa and Long Ridge fluorescence detectors, and surface array in hybrid mode
Mitsuhiro Abe, R. U. Abbasi, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, Jon Paul Lundquist, S. A. Blake, D. R. Bergman, 2020, izvirni znanstveni članek

Opis: Ultra high energy cosmic rays provide the highest known energy source in the universe to measure proton cross sections. Though conditions for collecting such data are less controlled than an accelerator environment, current generation cosmic ray observatories have large enough exposures to collect significant statistics for a reliable measurement for energies above what can be attained in the lab. Cosmic ray measurements of cross section use atmospheric calorimetry to measure depth of air shower maximum (Xmax), which is related to the primary particle’s energy and mass. The tail of the Xmax distribution is assumed to be dominated by showers generated by protons, allowing measurement of the inelastic proton-air cross section. In this work the proton-air inelastic cross section measurement, σ_inel_p−air, using data observed by Telescope Array’s Black Rock Mesa and Long Ridge fluorescence detectors and surface detector array in hybrid mode is presented. σ_inel_p−air is observed to be 520.1 ± 35.8 [Stat.] +25.0 −40 [Sys.] mb at √s = 73 TeV. The total proton-proton cross section is subsequently inferred from Glauber formalism and is found to be σ_tot_pp = 139.4 +23.4−21.3[Stat.] +15.0−24.0[Sys.] mb.
Najdeno v: osebi
Ključne besede: cosmic rays, astroparticles, proton-air cross section
Objavljeno: 04.02.2021; Ogledov: 671; Prenosov: 0
.pdf Polno besedilo (1,99 MB)

26.
Observations of the origin of downward terrestrial gamma-ray flashes
M. A. Stanley, R. U. Abbasi, R. LeVon, W. Rison, D. Rodeheffer, T. Abu-Zayyad, Jon Paul Lundquist, P. R. Krehbiel, J. Remington, J. W. Belz, 2020, izvirni znanstveni članek

Opis: In this paper we report the first close, high‐resolution observations of downward‐directed terrestrial gamma‐ray flashes (TGFs) detected by the large‐area Telescope Array cosmic ray observatory, obtained in conjunction with broadband VHF interferometer and fast electric field change measurements of the parent discharge. The results show that the TGFs occur during strong initial breakdown pulses (IBPs) in the first few milliseconds of negative cloud‐to‐ground and low‐altitude intracloud flashes and that the IBPs are produced by a newly identified streamer‐based discharge process called fast negative breakdown. The observations indicate the relativistic runaway electron avalanches (RREAs) responsible for producing the TGFs are initiated by embedded spark‐like transient conducting events (TCEs) within the fast streamer system and potentially also by individual fast streamers themselves. The TCEs are inferred to be the cause of impulsive sub‐pulses that are characteristic features of classic IBP sferics. Additional development of the avalanches would be facilitated by the enhanced electric field ahead of the advancing front of the fast negative breakdown. In addition to showing the nature of IBPs and their enigmatic sub‐pulses, the observations also provide a possible explanation for the unsolved question of how the streamer to leader transition occurs during the initial negative breakdown, namely, as a result of strong currents flowing in the final stage of successive IBPs, extending backward through both the IBP itself and the negative streamer breakdown preceding the IBP.
Najdeno v: osebi
Ključne besede: terrestrial gamma-ray flashes, lightning, fast breakdown, initial breakdown pulse, atmospheric electricity, transient conducting events
Objavljeno: 04.02.2021; Ogledov: 745; Prenosov: 3
URL Polno besedilo (0,00 KB)
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27.
Evidence for a supergalactic structure of magnetic deflection multiplets of ultra-high-energy cosmic rays
R. U. Abbasi, T. Abu-Zayyad, Mitsuhiro Abe, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy–angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Najdeno v: osebi
Ključne besede: extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray sources
Objavljeno: 05.02.2021; Ogledov: 742; Prenosov: 67
URL Polno besedilo (0,00 KB)
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28.
Search for large-scale anisotropy on arrival directions of ultra-high-energy cosmic rays observed with the telescope array experiment
Mitsuhiro Abe, R. U. Abbasi, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Motivated by the detection of a significant dipole structure in the arrival directions of ultra-high-energy cosmic rays above 8 EeV reported by the Pierre Auger Observatory (Auger), we search for a large-scale anisotropy using data collected with the surface detector array of the Telescope Array Experiment (TA). With 11 yr of TA data, a dipole structure in a projection of the R.A. is fitted with an amplitude of 3.3% ± 1.9% and a phase of 131° ± 33°. The corresponding 99% confidence-level upper limit on the amplitude is 7.3%. At the current level of statistics, the fitted result is compatible with both an isotropic distribution and the dipole structure reported by Auger.
Najdeno v: osebi
Ključne besede: cosmic rays, ultra-high-energy cosmic radiation, cosmic ray sources, cosmic ray showers, cosmic ray detectors, cosmic ray astronomy, extragalactic astronomy
Objavljeno: 05.02.2021; Ogledov: 677; Prenosov: 0
.pdf Polno besedilo (548,15 KB)

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