-
Search for Spatial Correlations of Neutrinos with Ultra-High-Energy Cosmic Rays
Authors:
The ANTARES collaboration,
A. Albert,
S. Alves,
M. André,
M. Anghinolfi,
M. Ardid,
S. Ardid,
J. -J. Aubert,
J. Aublin,
B. Baret,
S. Basa,
B. Belhorma,
M. Bendahman,
V. Bertin,
S. Biagi,
M. Bissinger,
J. Boumaaza,
M. Bouta,
M. C. Bouwhuis,
H. Brânzaş,
R. Bruijn,
J. Brunner,
J. Busto,
B. Caiffi,
D. Calvo
, et al. (1025 additional authors not shown)
Abstract:
For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for corre…
▽ More
For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data is provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above $\sim$50 EeV is provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrinos clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses has found a significant excess, and previously reported over-fluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs.
△ Less
Submitted 23 August, 2022; v1 submitted 18 January, 2022;
originally announced January 2022.
-
Observation of Variations in Cosmic Ray Single Count Rates During Thunderstorms and Implications for Large-Scale Electric Field Changes
Authors:
R. U. Abbasi,
T. Abu-Zayyad,
M. Allen,
Y. Arai,
R. Arimura,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
I. Buckland,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
R. Fukushima,
G. Furlich,
N. Globus,
R. Gonzalez,
W. Hanlon,
M. Hayashi
, et al. (140 additional authors not shown)
Abstract:
We present the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of cosmic ray single count rate intensity over a 700 km$^{2}$ area. Observations of variations in the secondary low-energy cosmic ray counting rate, using the TASD, allow us to study the electric field inside thunderstorms, on a large scale, as it progresses on top of t…
▽ More
We present the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of cosmic ray single count rate intensity over a 700 km$^{2}$ area. Observations of variations in the secondary low-energy cosmic ray counting rate, using the TASD, allow us to study the electric field inside thunderstorms, on a large scale, as it progresses on top of the 700 km$^{2}$ detector, without dealing with the limitation of narrow exposure in time and space using balloons and aircraft detectors. In this work, variations in the cosmic ray intensity (single count rate) using the TASD, were studied and found to be on average at the $\sim(0.5-1)\%$ and up to 2\% level. These observations were found to be both in excess and in deficit. They were also found to be correlated with lightning in addition to thunderstorms. These variations lasted for tens of minutes; their footprint on the ground ranged from 6 to 24 km in diameter and moved in the same direction as the thunderstorm. With the use of simple electric field models inside the cloud and between cloud to ground, the observed variations in the cosmic ray single count rate were recreated using CORSIKA simulations. Depending on the electric field model used and the direction of the electric field in that model, the electric field magnitude that reproduces the observed low-energy cosmic ray single count rate variations was found to be approximately between 0.2-0.4 GV. This in turn allows us to get a reasonable insight on the electric field and its effect on cosmic ray air showers inside thunderstorms.
△ Less
Submitted 18 November, 2021;
originally announced November 2021.
-
Indications of a Cosmic Ray Source in the Perseus-Pisces Supercluster
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
T. Abu-Zayyad,
M. Allen,
Y. Arai,
R. Arimura,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
I. Buckland,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
R. Fukushima,
G. Furlich,
N. Globus,
R. Gonzalez,
W. Hanlon
, et al. (135 additional authors not shown)
Abstract:
The Telescope Array Collaboration has observed an excess of events with $E \ge 10^{19.4} ~{\rm eV}$ in the data which is centered at (RA, dec) = ($19^\circ$, $35^\circ$). This is near the center of the Perseus-Pisces supercluster (PPSC). The PPSC is about $70 ~{\rm Mpc}$ distant and is the closest supercluster in the Northern Hemisphere (other than the Virgo supercluster of which we are a part). A…
▽ More
The Telescope Array Collaboration has observed an excess of events with $E \ge 10^{19.4} ~{\rm eV}$ in the data which is centered at (RA, dec) = ($19^\circ$, $35^\circ$). This is near the center of the Perseus-Pisces supercluster (PPSC). The PPSC is about $70 ~{\rm Mpc}$ distant and is the closest supercluster in the Northern Hemisphere (other than the Virgo supercluster of which we are a part). A Li-Ma oversampling analysis with $20^\circ$-radius circles indicates an excess in the arrival direction of events with a local significance of about 4 standard deviations. The probability of having such excess close to the PPSC by chance is estimated to be 3.5 standard deviations. This result indicates that a cosmic ray source likely exists in that supercluster.
△ Less
Submitted 27 October, 2021;
originally announced October 2021.
-
Surface detectors of the TAx4 experiment
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
Y. Arai,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
R. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
N. Hayashida,
K. Hibino
, et al. (124 additional authors not shown)
Abstract:
Telescope Array (TA) is the largest ultrahigh energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. It explores the origin of UHECRs by measuring their energy spectrum, arrival-direction distribution, and mass composition using a surface detector (SD) array covering approximately 700 km$^2$ and fluorescence detector (FD) stations. TA has found evidence for a cluster of cosmic rays with…
▽ More
Telescope Array (TA) is the largest ultrahigh energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. It explores the origin of UHECRs by measuring their energy spectrum, arrival-direction distribution, and mass composition using a surface detector (SD) array covering approximately 700 km$^2$ and fluorescence detector (FD) stations. TA has found evidence for a cluster of cosmic rays with energies greater than 57 EeV. In order to confirm this evidence with more data, it is necessary to increase the data collection rate.We have begun building an expansion of TA that we call TAx4. In this paper, we explain the motivation, design, technical features, and expected performance of the TAx4 SD. We also present TAx4's current status and examples of the data that have already been collected.
△ Less
Submitted 1 March, 2021;
originally announced March 2021.
-
Observations of the Origin of Downward Terrestrial Gamma-Ray Flashes
Authors:
J. W. Belz,
P. R. Krehbiel,
J. Remington,
M. A. Stanley,
R. U. Abbasi,
R. LeVon,
W. Rison,
D. Rodeheffer,
the Telescope Array Scientific Collaboration,
:,
T. Abu-Zayyad,
M. Allen,
E. Barcikowski,
D. R. Bergman,
S. A. Blake,
M. Byrne,
R. Cady,
B. G. Cheon,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich
, et al. (116 additional authors not shown)
Abstract:
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 (I…
▽ More
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.
△ Less
Submitted 12 October, 2020; v1 submitted 29 September, 2020;
originally announced September 2020.
-
Search for Large-scale Anisotropy on Arrival Directions of Ultra-high-energy Cosmic Rays Observed with the Telescope Array Experiment
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
N. Hayashida,
K. Hibino
, et al. (121 additional authors not shown)
Abstract:
Motivated by the detection of a significant dipole structure in the arrival directions of ultrahigh-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 years of TA data, a dipole structure in a projection of the right ascension is…
▽ More
Motivated by the detection of a significant dipole structure in the arrival directions of ultrahigh-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 years of TA data, a dipole structure in a projection of the right ascension is fitted with an amplitude of 3.3+- 1.9% and a phase of 131 +- 33 degrees. 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.
△ Less
Submitted 27 July, 2020; v1 submitted 30 June, 2020;
originally announced July 2020.
-
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
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
N. Hayashida,
K. Hibino,
R. Higuchi
, et al. (120 additional authors not shown)
Abstract:
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.…
▽ More
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 ($X_{\mathrm{max}}$), which is related to the primary particle's energy and mass. The tail of the $X_{\mathrm{max}}$ 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, $σ^{\mathrm{inel}}_{\mathrm{p-air}}$, using data observed by Telescope Array's Black Rock Mesa and Long Ridge fluorescence detectors and surface detector array in hybrid mode is presented. $σ^{\mathrm{inel}}_{\mathrm{p-air}}$ is observed to be $520.1 \pm 35.8$[Stat.] $^{+25.0}_{-40}$[Sys.]~mb at $\sqrt{s} = 73$ TeV. The total proton-proton cross section is subsequently inferred from Glauber formalism and is found to be $σ^{\mathrm{tot}}_{\mathrm{pp}} = 139.4 ^{+23.4}_{-21.3}$ [Stat.]$ ^{+15.0}_{-24.0}$[Sys.]~mb.
△ Less
Submitted 8 June, 2020;
originally announced June 2020.
-
Evidence for a Supergalactic Structure of Magnetic Deflection Multiplets of Ultra-High Energy Cosmic Rays
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
N. Hayashida,
K. Hibino
, et al. (119 additional authors not shown)
Abstract:
Evidence for a large-scale supergalactic cosmic ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high energy cosmic ray (UHECR) energies above 10$^{19}$ eV using seven 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 st…
▽ More
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 10$^{19}$ eV using seven 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, since the supergalactic plane is a fit to the average matter density of the local Large Scale Structure (LSS), 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 TA (the hotspot and coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data post-trial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2$σ$. The ten years of data post-trial significance is 4.1$σ$. 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.
△ Less
Submitted 2 July, 2020; v1 submitted 14 May, 2020;
originally announced May 2020.
-
Search for Ultra-High-Energy Neutrinos with the Telescope Array Surface Detector
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda
, et al. (112 additional authors not shown)
Abstract:
We present an upper limit on the flux of ultra-high-energy down-going neutrinos for $E > 10^{18}\ \mbox{eV}$ 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 p…
▽ More
We present an upper limit on the flux of ultra-high-energy down-going neutrinos for $E > 10^{18}\ \mbox{eV}$ 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.
△ Less
Submitted 12 May, 2020; v1 submitted 9 May, 2019;
originally announced May 2019.
-
Search for point sources of ultra-high energy photons with the Telescope Array surface detector
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. diMatteo,
T. Fujii,
K. Fujita,
R. Fujiwara,
M. Fukushima,
G. Furlich,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino
, et al. (114 additional authors not shown)
Abstract:
The surface detector (SD) of the Telescope Array (TA) experiment allows one to indirectly detect photons with energies of order $10^{18}$ eV and higher and to separate photons from the cosmic-ray background. In this paper we present the results of a blind search for point sources of ultra-high energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers (…
▽ More
The surface detector (SD) of the Telescope Array (TA) experiment allows one to indirectly detect photons with energies of order $10^{18}$ eV and higher and to separate photons from the cosmic-ray background. In this paper we present the results of a blind search for point sources of ultra-high energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers (EAS) are separated from the hadron-induced EAS background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment's angular resolution for photons. Average 95% C.L. upper limits for the point-source flux of photons with energies greater than $10^{18}$, $10^{18.5}$, $10^{19}$, $10^{19.5}$ and $10^{20}$ eV are $0.094$, $0.029$, $0.010$, $0.0073$ and $0.0058$ km$^{-2}$yr$^{-1}$ respectively. For the energies higher than $10^{18.5}$ eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.
△ Less
Submitted 9 March, 2020; v1 submitted 30 March, 2019;
originally announced April 2019.
-
Constraints on the diffuse photon flux with energies above $10^{18}$ eV using the surface detector of the Telescope Array experiment
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino
, et al. (118 additional authors not shown)
Abstract:
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 wav…
▽ More
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 $0.067$, $0.012$, $0.0036$, $0.0013$, $0.0013~\mbox{km}^{-2}\mbox{yr}^{-1}\mbox{sr}^{-1}$ correspondingly.
△ Less
Submitted 19 March, 2019; v1 submitted 9 November, 2018;
originally announced November 2018.
-
Testing a reported correlation between arrival directions of ultrahigh-energy cosmic rays and a flux pattern from nearby starburst galaxies using Telescope Array data
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino
, et al. (117 additional authors not shown)
Abstract:
The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did n…
▽ More
The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did not optimize the parameter values but kept them fixed to the best-fit values found by Auger, namely 9.7% for the anisotropic fraction of cosmic rays assumed to originate from the SBGs in the list and 12.9° for the angular scale of the correlations. The energy threshold we adopted is 43 EeV, corresponding to 39 EeV in Auger when taking into account the energy-scale difference between two experiments. We find that the TA data is compatible with isotropy to within 1.1σ and with the Auger result to within 1.4σ, meaning that it is not capable to discriminate between these two hypotheses.
△ Less
Submitted 22 October, 2018; v1 submitted 5 September, 2018;
originally announced September 2018.
-
Mass composition of ultra-high-energy cosmic rays with the Telescope Array Surface Detector Data
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino
, et al. (118 additional authors not shown)
Abstract:
The results on ultra-high-energy cosmic rays (UHECR) mass composition obtained with the Telescope Array surface detector are presented. The analysis employs the boosted decision tree (BDT) multivariate analysis built upon 14 observables related to both the properties of the shower front and the lateral distribution function. The multivariate classifier is trained with Monte-Carlo sets of events in…
▽ More
The results on ultra-high-energy cosmic rays (UHECR) mass composition obtained with the Telescope Array surface detector are presented. The analysis employs the boosted decision tree (BDT) multivariate analysis built upon 14 observables related to both the properties of the shower front and the lateral distribution function. The multivariate classifier is trained with Monte-Carlo sets of events induced by the primary protons and iron. An average atomic mass of UHECR is presented for energies $10^{18.0}-10^{20.0}\ \mbox{eV}$. The average atomic mass of primary particles shows no significant energy dependence and corresponds to $\langle \ln A \rangle = 2.0 \pm 0.1 (stat.) \pm 0.44 (syst.)$. The result is compared to the mass composition obtained by the Telescope Array with $\mbox{X}_{\mbox{max}}$ technique along with the results of other experiments. Possible systematic errors of the method are discussed.
△ Less
Submitted 24 January, 2019; v1 submitted 10 August, 2018;
originally announced August 2018.
-
Study of muons from ultra-high energy cosmic ray air showers measured with the Telescope Array experiment
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. Di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino
, et al. (117 additional authors not shown)
Abstract:
One of the uncertainties in interpretation of ultra-high energy cosmic ray (UHECR) data comes from the hadronic interaction models used for air shower Monte Carlo (MC) simulations. The number of muons observed at the ground from UHECR-induced air showers is expected to depend upon the hadronic interaction model. One may therefore test the hadronic interaction models by comparing the measured numbe…
▽ More
One of the uncertainties in interpretation of ultra-high energy cosmic ray (UHECR) data comes from the hadronic interaction models used for air shower Monte Carlo (MC) simulations. The number of muons observed at the ground from UHECR-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 UHE extensive air showers obtained by analyzing the signal of surface detector stations which should have high $\it{muon \, purity}$. The muon purity of a station will depend on both the inclination of the shower and the relative position of the station. In 7 years' data from the Telescope Array experiment, we find that the number of particles observed for signals with an expected muon purity of $\sim$65% at a lateral distance of 2000 m from the shower core is $1.72 \pm 0.10{\rm (stat.)} \pm 0.37 {\rm (syst.)}$ 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 $1.67 \pm 0.10 \pm 0.36$ 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.
△ Less
Submitted 11 April, 2018;
originally announced April 2018.
-
The Cosmic-Ray Energy Spectrum between 2 PeV and 2 EeV Observed with the TALE detector in monocular mode
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. Di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda
, et al. (116 additional authors not shown)
Abstract:
We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector. The TALE air fluorescence detector is also sensitive to the Cherenkov light produced by shower particles. Low energy cosmic rays, in the PeV energy range, are detectable by TALE as "Cherenkov Events". Using these events, we measure the energy spectrum from a lo…
▽ More
We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector. The TALE air fluorescence detector is also sensitive to the Cherenkov light produced by shower particles. Low energy cosmic rays, in the PeV energy range, are detectable by TALE as "Cherenkov Events". Using these events, we measure the energy spectrum from a low energy of $\sim 2$ PeV to an energy greater than 100 PeV. Above 100 PeV TALE can detect cosmic rays using air fluorescence. This allows for the extension of the measurement to energies greater than a few EeV. In this paper, we will describe the detector, explain the technique, and present results from a measurement of the spectrum using $\sim 1000$ hours of observation. The observed spectrum shows a clear steepening near $10^{17.1}$ eV, along with an ankle-like structure at $10^{16.2}$ eV. These features present important constraints on galactic cosmic rays origin and propagation models. The feature at $10^{17.1}$ eV may also mark the end of the galactic cosmic rays flux and the start of the transition to extra-galactic sources.
△ Less
Submitted 3 March, 2018;
originally announced March 2018.
-
Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E$\geq$10$^{19.2}$ eV with the Telescope Array Surface Detector
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
A. Di Matteo,
T. Fujii,
K. Fujita,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
M. Hayashi,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda
, et al. (115 additional authors not shown)
Abstract:
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 data from the Telescope Array surface detector. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson l…
▽ More
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 data from the Telescope Array surface detector. 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 $9^h$$16^m$, $45^{\circ}$. and has a deficit of events with energies $10^{19.2}$$\leq$$E$$<$$10^{19.75}$ eV and an excess for $E$$\geq$$10^{19.75}$ eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be $9$$\times$$10^{-5}$ ($3.74$$σ_{global}$).
△ Less
Submitted 17 February, 2018; v1 submitted 14 February, 2018;
originally announced February 2018.
-
Evidence for Declination Dependence of the Ultrahigh Energy Cosmic Ray Spectrum in the Northern Hemisphere
Authors:
R. U. Abbasi,
T. Abu-Zayyad,
M. Allen,
Y. Arai,
R. Arimura,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
I. Buckland,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
K. Fujisue,
K. Fujita,
R. Fujiwara,
M. Fukushima,
R. Fukushima,
G. Furlich,
N. Globus,
R. Gonzalez,
W. Hanlon,
M. Hayashi
, et al. (134 additional authors not shown)
Abstract:
Telescope Array (TA) is the largest experiment in the Northern Hemisphere studying ultrahigh energy cosmic rays. TA measurements of the cosmic ray spectrum using the surface detector have the best statistical power in the experiment, and observe the ankle of the spectrum and the high energy cutoff. When the data are divided into two declination bands, above and below 24.8 degrees, the cutoff appea…
▽ More
Telescope Array (TA) is the largest experiment in the Northern Hemisphere studying ultrahigh energy cosmic rays. TA measurements of the cosmic ray spectrum using the surface detector have the best statistical power in the experiment, and observe the ankle of the spectrum and the high energy cutoff. When the data are divided into two declination bands, above and below 24.8 degrees, the cutoff appears at $10^{19.64 \pm 0.04}$ ($10^{19.84 \pm 0.02}$) eV in the lower (higher) band, an energy difference of 58\%. The global significance of the difference is 4.3 standard deviations. The lack of an instrumental cause of this difference implies it is astrophysical in nature.
△ Less
Submitted 10 November, 2021; v1 submitted 23 January, 2018;
originally announced January 2018.
-
Search for Anisotropy in the Ultra High Energy Cosmic Ray Spectrum using the Telescope Array Surface Detector
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
M. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda,
N. Inoue,
T. Ishii
, et al. (106 additional authors not shown)
Abstract:
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…
▽ More
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 $\pm 30^\circ$ 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 $6.2\pm1.1\times10^{-4}$ ($3.2σ$) 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.
△ Less
Submitted 10 August, 2017; v1 submitted 16 July, 2017;
originally announced July 2017.
-
Gamma-ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
Authors:
R. U. Abbasi,
T. Abu-Zayyad,
M. Allen,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
M. Byrne,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
M. Fukushima,
G. Furlich,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda,
N. Inoue,
T. Ishii,
H. Ito
, et al. (99 additional authors not shown)
Abstract:
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~square kilometer cosmic ray observatory located in southwestern Utah, U.S.A. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-pro…
▽ More
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~square kilometer cosmic ray observatory located in southwestern Utah, U.S.A. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-producing flashes were obtained with a 3D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases co-located with the TASD. National Lightning Detection Network (NLDN) information was also used throughout. The showers arrived in a sequence of 2--5 short-duration ($\le$10~$μ$s) bursts over time intervals of several hundred microseconds, and originated at an altitude of $\simeq$3--5 kilometers 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 $\simeq$$10^{12}$--$10^{14}$ photons for $16^{\circ}$ half-angle beams. We conclude that the showers are terrestrial gamma-ray flashes (TGFs), 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 TGFs.
△ Less
Submitted 18 May, 2018; v1 submitted 17 May, 2017;
originally announced May 2017.
-
Search for EeV Protons of Galactic Origin
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
B. G. Cheon,
J. Chiba,
M. Chikawa,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
M. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda,
N. Inoue,
T. Ishii
, et al. (105 additional authors not shown)
Abstract:
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…
▽ More
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$^\circ$ in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50$^\circ$ 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.
△ Less
Submitted 26 October, 2016; v1 submitted 22 August, 2016;
originally announced August 2016.
-
First Upper Limits on the Radar Cross Section of Cosmic-Ray Induced Extensive Air Showers
Authors:
R. U. Abbasi,
M. Abe,
M. Abou Bakr Othman,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
D. Besson,
S. A. Blake,
M. Byrne,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
B. Farhang-Boroujeny,
T. Fujii,
M. Fukushima,
W. H. Gillman,
T. Goto,
W. Hanlon
, et al. (114 additional authors not shown)
Abstract:
TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of v…
▽ More
TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data since 2013 with the primary goal of observing the radar signatures of extensive air showers (EAS). Simulations indicate that echoes are expected to be short in duration (~10 microseconds) and exhibit rapidly changing frequency, with rates on the order of 1 MHz/microsecond. The EAS radar cross-section (RCS) is currently unknown although it is the subject of over 70 years of speculation. A novel signal search technique is described in which the expected radar echo of a particular air shower is used as a matched filter template and compared to waveforms obtained by triggering the radar DAQ using the Telescope Array fluorescence detector. No evidence for the scattering of radio frequency radiation by EAS is obtained to date. We report the first quantitative RCS upper limits using EAS that triggered the Telescope Array Fluorescence Detector.
△ Less
Submitted 16 March, 2016;
originally announced March 2016.
-
Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array
Authors:
The IceCube Collaboration,
M. G. Aartsen,
K. Abraham,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
M. Ahrens,
D. Altmann,
T. Anderson,
I. Ansseau,
M. Archinger,
C. Arguelles,
T. C. Arlen,
J. Auffenberg,
X. Bai,
S. W. Barwick,
V. Baum,
R. Bay,
J. J. Beatty,
J. Becker Tjus,
K. -H. Becker,
E. Beiser,
P. Berghaus,
D. Berley
, et al. (848 additional authors not shown)
Abstract:
This paper presents the results of different searches for correlations between very high-energy neutrino candidates detected by IceCube and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array. We first consider samples of cascade neutrino events and of high-energy neutrino-induced muon tracks, which provided evidence for a neutrino flux of astrophysical…
▽ More
This paper presents the results of different searches for correlations between very high-energy neutrino candidates detected by IceCube and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array. We first consider samples of cascade neutrino events and of high-energy neutrino-induced muon tracks, which provided evidence for a neutrino flux of astrophysical origin, and study their cross-correlation with the ultrahigh-energy cosmic ray (UHECR) samples as a function of angular separation. We also study their possible directional correlations using a likelihood method stacking the neutrino arrival directions and adopting different assumptions on the size of the UHECR magnetic deflections. Finally, we perform another likelihood analysis stacking the UHECR directions and using a sample of through-going muon tracks optimized for neutrino point-source searches with sub-degree angular resolution. No indications of correlations at discovery level are obtained for any of the searches performed. The smallest of the p-values comes from the search for correlation between UHECRs with IceCube high-energy cascades, a result that should continue to be monitored.
△ Less
Submitted 21 January, 2016; v1 submitted 30 November, 2015;
originally announced November 2015.
-
The IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array: Joint Contribution to the 34th International Cosmic Ray Conference (ICRC 2015)
Authors:
IceCube Collaboration,
M. G. Aartsen,
K. Abraham,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
M. Ahrens,
D. Altmann,
T. Anderson,
I. Ansseau,
M. Archinger,
C. Arguelles,
T. C. Arlen,
J. Auffenberg,
X. Bai,
S. W. Barwick,
V. Baum,
R. Bay,
J. J. Beatty,
J. Becker Tjus,
K. -H. Becker,
E. Beiser,
S. BenZvi,
P. Berghaus
, et al. (869 additional authors not shown)
Abstract:
We have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube `high-energy starting events' sample and the other with 16 high-energy `track events'. The angular…
▽ More
We have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube `high-energy starting events' sample and the other with 16 high-energy `track events'. The angular separation between the arrival directions of neutrinos and UHECRs is scanned over. The same events are also used in a separate search using a maximum likelihood approach, after the neutrino arrival directions are stacked. To estimate the significance we assume UHECR magnetic deflections to be inversely proportional to their energy, with values $3^\circ$, $6^\circ$ and $9^\circ$ at 100 EeV to allow for the uncertainties on the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube sample of through-going muon track events which were optimized for neutrino point-source searches.
△ Less
Submitted 6 November, 2015;
originally announced November 2015.
-
Pierre Auger Observatory and Telescope Array: Joint Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)
Authors:
Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda
, et al. (553 additional authors not shown)
Abstract:
Joint contributions of the Pierre Auger Collaboration and the Telescope Array Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.
Joint contributions of the Pierre Auger Collaboration and the Telescope Array Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.
△ Less
Submitted 6 November, 2015;
originally announced November 2015.
-
Measurement of the Proton-Air Cross Section with Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda
, et al. (101 additional authors not shown)
Abstract:
In this work we are reporting on the measurement of the proton-air inelastic cross section $σ^{\rm inel}_{\rm p-air}$ using the Telescope Array (TA) detector. Based on the measurement of the $σ^{\rm inel}_{\rm p-air}$ the proton-proton cross section $σ_{\rm p-p}$ value is also determined at $\sqrt{s} = 95_{-8}^{+5}$ TeV. Detecting cosmic ray events at ultra high energies with Telescope Array enabl…
▽ More
In this work we are reporting on the measurement of the proton-air inelastic cross section $σ^{\rm inel}_{\rm p-air}$ using the Telescope Array (TA) detector. Based on the measurement of the $σ^{\rm inel}_{\rm p-air}$ the proton-proton cross section $σ_{\rm p-p}$ value is also determined at $\sqrt{s} = 95_{-8}^{+5}$ TeV. Detecting cosmic ray events at ultra high energies with Telescope Array enables us to study this fundamental parameter that we are otherwise unable to access with particle accelerators. The data used in this report is the hybrid events observed by the Middle Drum fluorescence detector together with the surface array detector collected over five years. The value of the $σ^{\rm inel}_{\rm p-air}$ is found to be equal to $567.0 \pm 70.5 [{\rm Stat.}] ^{+29}_{-25} [{\rm Sys.}]$ mb. The total proton-proton cross section is subsequently inferred from Glauber Formalism and Block, Halzen and Stanev QCD inspired fit and is found to be equal to $170_{-44}^{+48} [{\rm Stat.}] _{-17}^{+19} [{\rm Sys.}] $mb.
△ Less
Submitted 31 August, 2015; v1 submitted 7 May, 2015;
originally announced May 2015.
-
Searches for Large-Scale Anisotropy in the Arrival Directions of Cosmic Rays Detected above Energy of $10^{19}$ eV at the Pierre Auger Observatory and the Telescope Array
Authors:
The Pierre Auger,
Telescope Array Collaborations,
:,
A. Aab,
P. Abreu,
M. Aglietta,
E. J. Ahn,
I. Al Samarai,
I. F. M. Albuquerque,
I. Allekotte,
J. Allen,
P. Allison,
A. Almela,
J. Alvarez Castillo,
J. Alvarez-Muñiz,
R. Alves Batista,
M. Ambrosio,
A. Aminaei,
L. Anchordoqui,
S. Andringa,
C. Aramo,
F. Arqueros,
H. Asorey,
P. Assis,
J. Aublin
, et al. (584 additional authors not shown)
Abstract:
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array…
▽ More
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above $10^{19}$ eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above $10^{19}$ eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.
△ Less
Submitted 10 September, 2014;
originally announced September 2014.
-
Study of Ultra-High Energy Cosmic Ray Composition Using Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda
, et al. (102 additional authors not shown)
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…
▽ More
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 Xmax 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.
△ Less
Submitted 5 November, 2014; v1 submitted 7 August, 2014;
originally announced August 2014.
-
A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array Experiment
Authors:
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda,
D. Ikeda
, et al. (101 additional authors not shown)
Abstract:
We report on the search for steady point-like sources of neutral particles around 10$^{18}$ eV between 2008 May and 2013 May with the scintillator surface detector 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 wa…
▽ More
We report on the search for steady point-like sources of neutral particles around 10$^{18}$ eV between 2008 May and 2013 May with the scintillator surface detector 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 $E>1$ EeV 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.
△ Less
Submitted 3 March, 2015; v1 submitted 23 July, 2014;
originally announced July 2014.
-
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 Experiment
Authors:
The Telescope Array Collaboration,
R. U. Abbasi,
M. Abe,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W. Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
T. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda
, et al. (102 additional authors not shown)
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$^\circ$-radius circles. The hotspot has a Li-Ma stati…
▽ More
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$^\circ$-radius circles. The hotspot has a Li-Ma statistical significance of 5.1$σ$, and is centered at R.A.=146.7$^{\circ}$, Dec.=43.2$^{\circ}$. The position of the hotspot is about 19$^{\circ}$ off of the supergalactic plane. The probability of a cluster of events of 5.1$σ$ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7$\times$10$^{-4}$ (3.4$σ$).
△ Less
Submitted 16 July, 2014; v1 submitted 23 April, 2014;
originally announced April 2014.
-
Pierre Auger Observatory and Telescope Array: Joint Contributions to the 33rd International Cosmic Ray Conference (ICRC 2013)
Authors:
The Telescope Array,
Pierre Auger Collaborations,
:,
T. Abu-Zayyad,
M. Allen,
R. Anderson,
R. Azuma,
E. Barcikowski,
J. W Belz,
D. R. Bergman,
S. A. Blake,
R. Cady,
M. J. Chae,
B. G. Cheon,
J. Chiba,
M. Chikawa,
W. R. Cho,
T. Fujii,
M. Fukushima,
K. Goto,
W. Hanlon,
Y. Hayashi,
N. Hayashida,
K. Hibino,
K. Honda
, et al. (598 additional authors not shown)
Abstract:
Joint contributions of the Pierre Auger and Telescope Array Collaborations to the 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, July 2013: cross-calibration of the fluorescence telescopes, large scale anisotropies and mass composition.
Joint contributions of the Pierre Auger and Telescope Array Collaborations to the 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, July 2013: cross-calibration of the fluorescence telescopes, large scale anisotropies and mass composition.
△ Less
Submitted 2 October, 2013;
originally announced October 2013.