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1.
Azimuthal asymmetry in the risetime of the Surface Detector signals of the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Ignacio Minaya, 2015, objavljeni znanstveni prispevek na konferenci

Opis: The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable sensitive to the mass composition of cosmic rays above 3 × 10[sup]18 eV. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJetII- 04 and Epos-LHC) an indication that the mean cosmic-ray mass increases with energy, as has been inferred from other studies. However the absolute values derived for the mass are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modelling that must be resolved before the mass composition can be inferred from (sec θ)max.
Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, Surface Detector, risetime of detector signal, azimuthal asymmetry, extensive air showers
Objavljeno: 03.03.2016; Ogledov: 1813; Prenosov: 106
.pdf Polno besedilo (243,04 KB)

2.
Solar Cycle Modulation of Cosmic Rays Observed with the Low Energy Modes of the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Jimmy Masías-Meza, 2015, objavljeni znanstveni prispevek na konferenci

Opis: The low energy modes of the surface detector array of the Pierre Auger Observatory record variations in the flux of low energy secondary particles with extreme detail. These two modes consist of recording (1) the rate of signals for energies between ∼15 MeV and ∼100 MeV (the Scaler mode) and (2) the calibration charge histograms of the individual pulses detected by each water-Cherenkov station, covering different energy channels up to ∼1 GeV (the Histogram mode). Previous work has studied the flux of galactic cosmic rays on short and intermediate time scales (i.e. from minutes to weeks) using these low energy modes. In this work, after including a long- term correction to the response of the detectors, we present the first long-term analysis of the flux of cosmic rays using scalers and two energy bands of the calibration histograms. We show its sensitivity to the solar cycle variation and its relation to the solar modulation of cosmic rays for an 8-year period.
Najdeno v: ključnih besedah
Povzetek najdenega: ...The low energy modes of the surface detector array of the Pierre Auger Observatory record...
Ključne besede: Pierre Auger Observatory, Surface Detector, secondary cosmic rays, scaler mode, charge histogram mode, solar cycle modulation
Objavljeno: 03.03.2016; Ogledov: 1810; Prenosov: 115
.pdf Polno besedilo (533,18 KB)

3.
Improved limits to point-like sources of ultrahigh energy neutrinos with the Pierre Auger Observatory
Lili Yang, Marta Trini, Pablo Pieroni, Jaime Alvarez-Muniz, 2016, elaborat, predštudija, študija

Najdeno v: ključnih besedah
Povzetek najdenega: ...ultrahigh energy neutrinos, Pierre Auger Observatory, surface detector...
Ključne besede: ultrahigh energy neutrinos, Pierre Auger Observatory, surface detector
Objavljeno: 07.04.2016; Ogledov: 1861; Prenosov: 0
.pdf Polno besedilo (307,54 KB)

4.
Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, A. Aab, 2016, izvirni znanstveni članek

Opis: The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable, (secθ)max, sensitive to the mass composition of cosmic rays above 3×1018  eV. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass increases slowly with energy, as has been inferred from other studies. However, the mass estimates are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modeling that must be resolved before the mass composition can be inferred from (secθ)max.
Najdeno v: ključnih besedah
Ključne besede: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, extensive air showers, Auger Surface Detector signals risetime, azimuthal symmetry
Objavljeno: 15.04.2016; Ogledov: 2202; Prenosov: 0
.pdf Polno besedilo (698,19 KB)

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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: 151; Prenosov: 8
.pdf Polno besedilo (169,05 KB)

9.
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: ...It consists of an array of 507 surface detectors (SD) covering a total 700 km^2...
Ključne besede: cosmic radiation, UHE detector, fluorescence detector, surface, Telescope Array Experiment, anisotropy, experimental results
Objavljeno: 28.04.2020; Ogledov: 143; Prenosov: 8
.pdf Polno besedilo (1,88 MB)

10.
Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700‐km^2 cosmic ray observatory located in southwestern Utah, USA. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower‐producing flashes were obtained with a 3‐D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the TASD. National Lightning Detection Network information was also used throughout. The showers arrived in a sequence of 2–5 short‐duration (≤10 μs) bursts over time intervals of several hundred microseconds and originated at an altitude of ≃3–5 km above ground level during the first 1–2 ms of downward negative leader breakdown at the beginning of cloud‐to‐ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward‐beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of ≃10^12–10^14 photons for 16° half‐angle beams. We conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground‐based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes.
Najdeno v: ključnih besedah
Povzetek najdenega: ...in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700‐km^2...
Ključne besede: gamma rays, lightning, gamma ray bursts, surface detector
Objavljeno: 30.04.2020; Ogledov: 203; Prenosov: 0
.pdf Polno besedilo (1,14 MB)

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