251. Study of Ultra-High Energy Cosmic Ray composition using Telescope Array’s Middle Drum detector and surface array in hybrid modeR.U. Abbasi, Jon Paul Lundquist, 2015, original scientific article Abstract: 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.
Keywords: Ultra-High Energy Cosmic Rays, Cosmic ray composition, Atmospheric fluorescence, Extensive air shower array, Hybrid, Telescope Array
Published in RUNG: 24.04.2020; Views: 3019; Downloads: 0
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252. Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays E ≥ 10^19.2 eV with the Telescope Array Surface DetectorR.U. Abbasi, Jon Paul Lundquist, 2018, original scientific article Abstract: Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector 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 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).
Keywords: astroparticle physics, cosmic rays, anisotropy, large-scale structure of universe
Published in RUNG: 24.04.2020; Views: 3019; Downloads: 196
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253. Eenergy Anisotropies of Proton-like Ultra-High Energy Cosmic RaysJon Paul Lundquist, doctoral dissertation Abstract: Evidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA “Hotspot” excess, E≥10^19.75 eV, is found to correspond to a deficit, or “Coldspot,” of events for 10^19.1≤E<10^19.75 eV at 142◦R.A., 40◦ Dec. The global post-trial significance of this Hot/Coldspot event density asymmetry is found to be 5.1σ (p = 1.56 × 10−7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74σ significance for energies E≥10^19.2 eV and an energy-distance correlation with a 3.34σ significance for energies E≥1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65σ significance (E≥1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new “Quality Factor Analysis” pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean shower depth distribution is developed – as there is large disagreement in between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E≥10^18.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields.
Keywords: cosmic rays, UHECR, composition, anisotropy
Published in RUNG: 24.04.2020; Views: 2904; Downloads: 0
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254. Radar Sensing of Ultra-High Energy Cosmic Ray ShowersJon Paul Lundquist, undergraduate thesis Abstract: The intent of this paper is to review the history and potential importance of the use of radar techniques in detecting the ionization columns of ultra-high energy cosmic ray showers and give a short overview of a currently planned radar experiment at the Telescope Array. There is much activity in cosmic ray research to study the composition and source locations of this phenomena. Radar would be an important addition to fluorescence and scintillation detection as it theoretically could attain greater volume coverage and nearly the accuracy of fluorescence systems with less infrastructure and much longer running times. The currently estimated mean echo lifetime is on the order of 50 µs for a cosmic ray of energy 10^19 eV. It is shown that a continuous wave bi-directional radar system transmitting in the low-VHF with a large obstruction between receiver and transmitter (such as a mountain or earth curvature), which assures direct transmission is reduced, is the nominal configuration and the planned radar experiment at the Telescope Array satisfies these requirements.
Keywords: cosmic rays, radar
Published in RUNG: 24.04.2020; Views: 2829; Downloads: 0
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255. A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array ExperimentR.U. Abbasi, Jon Paul Lundquist, 2015, original scientific article Abstract: We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013
May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess
above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic
sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the
neutron flux that corresponds to an averaged flux of 0.07 km−2 yr−1 for E > 1EeV in the northern sky at the 95%
confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources.
The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km−2 yr−1 for
E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.
Keywords: acceleration of particles, cosmic rays, surveys
Published in RUNG: 24.04.2020; Views: 3611; Downloads: 0
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256. Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array ExperimentR.U. Abbasi, Jon Paul Lundquist, 2014, original scientific article Abstract: We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20∘-radius circles. The hotspot has a Li-Ma statistical significance of 5.1σ, and is centered at R.A.=146.7∘, Dec.=43.2∘. The position of the hotspot is about 19∘ off of the supergalactic plane. The probability of a cluster of events of 5.1σ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7×10−4 (3.4σ).
Keywords: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Published in RUNG: 24.04.2020; Views: 3076; Downloads: 0
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258. SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORYMarta Trini, 2019, doctoral dissertation Abstract: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to
answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory
is the largest experiment that can detect the extensive air showers produced when the cosmic rays and
neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector
of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis
we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers
produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the
inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in
the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply-
penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in
this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined
events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov
stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We
have established a complete chain of criteria to first select the inclined events among the sample of all
events triggering the Infilled array, and then identifying those that have a large electromagnetic component
at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the
so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino
identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of
the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to
be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also
computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017.
Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in
the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in
the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor,
k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Keywords: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled
array
Published in RUNG: 03.10.2019; Views: 4848; Downloads: 147
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259. Space weather research with the Pierre Auger ObservatoryMiha Živec, 2019, master's thesis Abstract: Space weather refers to environmental conditions in the interplanetary space and Earth’s
magnetosphere, ionosphere and exosphere and can influence the performance and reliability
of electronics based technological systems. The major role in space weather
changes plays the solar wind, a stream of charged particles (mostly electrons and protons)
with energies of approximately 1 keV, that can cause geomagnetic storms and auroras.
During their entry into the atmosphere, high energy cosmic rays collide with atomic
nuclei of atmospheric gasses. When scattering occurs extensive air showers are created.
Those cascades of secondary particles create flashes of light due to the Cherenkov
effect as well as excite molecules of nitrogen gas in atmosphere, which then glow in
fluorescent light. In order to observe the light created by air showers, it has to be
collected with telescopes. The particles from the cascades that reach ground can be
detected with surface detectors. The Pierre Auger Observatory is the largest observatory
for cosmic ray measurements. It is located in Argentinian pampas covering an area of
3000 km2. It consists of 1660 surface detectors and 27 fluorescence telescopes. For
cosmic rays with energies above few 1017 eV, a precise reconstruction of energy and
direction of primary particle is achievable. Observatory also allows measurement of
flux of incoming particles down to primary energies in ca. 10 GeV - 10 TeV interval, with a median energy ca. 80-90 GeV. This measurement capability is called "scaler"
mode, since the corresponding data consist of scaler counted cascade particles with
deposited energy between 15 and 100 MeV, at the average rate of 2 kHz per individual
surface detector.
For the purpose of this master thesis I compared the data from scaler mode measurements
with measurements of neutron monitors, which are commonly used for space weather
observations. With the correlation received from the comparison, I showed that scaler
mode operation of Pierre Auger observatory can be used to monitor space weather events
such as solar cycle and the decreases in the observed galactic cosmic ray intensity due
to solar wind (Forbush decrease).
Keywords: Pierre Auger Observatory, cosmic rays, space weather, Forbush decrease
Published in RUNG: 17.09.2019; Views: 5071; Downloads: 181
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260. Mass composition of cosmic rays with energies from 10^17.2 eV to 10^20 eV using surface and fluorescence detectors of the Pierre Auger ObservatoryGašper Kukec Mezek, 2018, published scientific conference contribution Abstract: Ultra-high-energy cosmic rays (UHECRs) are highly energetic particles with EeV energies, exceeding the capabilities of man-made colliders. They hold information on extreme astrophysical processes that create them and the medium they traverse on their way towards Earth. However, their mass composition at such energies is still unclear, because data interpretation depends on our choice of high energy hadronic interaction models. With its hybrid detection method, the Pierre Auger Observatory has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations (SD) and fluorescence telescopes (FD). We present recent mass composition results from the Pierre Auger Collaboration using observational parameters from SD and FD measurements. Using the full dataset of the Pierre Auger Observatory, implications on composition can be made for energies above 10^17.2 eV.
Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Published in RUNG: 24.05.2019; Views: 3400; Downloads: 110
Full text (573,00 KB) |
