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1. Measurements of Cosmic Ray Mass Composition with the IceCube Neutrino Observatory

   https://doi.org/10.1051/epjconf/202328302007  

   Plum, Matthias ( January 2023 , EPJ Web of Conferences)

   De Mitri, I. ; Barbato, F.C.T. ; Boncioli, D. ; Evoli, C. ; Pagliaroli, G. ; Salamida, F. (Ed.)

   The IceCube Neutrino Observatory is a multi-component detector at the South Pole. Besides studying high-energy neutrinos, it is capable of measuring high-energy cosmic rays from PeV to EeV. This energy region is thought to cover the transition from galactic to extragalactic sources of cosmic rays. The observatory consists of the deep in-ice IceCube array, which measures the high-energy (≥500 GeV) muonic component, and the IceTop surface array, which is sensitive to the electromagnetic and low-energy muonic part of an air shower. The primary energy and the mass composition can be measured simultaneously by applying statistical methods including modern machine-learning techniques to reconstruct cosmic ray air showers. In this contribution, we will discuss recent improvements to the reconstruction techniques, the mass composition sensitivity, and an outlook on future improved measurements with the full surface scintillator/radio array to mitigate snow accumulation and measure the air shower maximum X max using imaging air-Cherenkov telescopes IceAct. 

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2. High-altitude characterization of the Hunga pressure wave with cosmic rays by the HAWC observatory

   https://doi.org/10.1016/j.asr.2023.09.049  

   Alfaro, Ruben ; Alvarez, César ; Arteaga-Velázquez, Juan Carlos ; Kollamparambil_Paul, Arun Babu ; Rojas, Daniel Avila ; Ayala_Solares, Hugo Alberto ; Babu, Rishi ; Belmont-Moreno, Ernesto ; Brisbois, Chad ; Caballero-Mora, Karen S ; et al ( January 2024 , Advances in Space Research)

   High-energy cosmic rays that hit the Earth can be used to study large-scale atmospheric perturbations. After a first interaction in the upper parts of the atmosphere, cosmic rays produce a shower of particles that sample it down to the detector level. The HAWC (High-Altitude Water Cherenkov) gamma-ray observatory in Central Mexico at 4,100 m elevation detects air shower particles continuously with 300 water Cherenkov detectors with an active area of 12,500 m2. On January 15th, 2022, HAWC detected the passage of the pressure wave created by the explosion of the Hunga volcano in the Tonga islands, 9,000 km away, as an anomaly in the measured rate of shower particles. The HAWC measurements are used to determine the propagation speed of four pressure wave passages, and correlate the variations of the shower particle rates with the barometric pressure changes. The profile of the shower particle rate and atmospheric pressure variations for the first transit of the pressure wave at HAWC is compared to the pressure measurements at the Tonga island, near the volcanic explosion. By using the cosmic-ray propagation in the atmosphere as a probe for the pressure, it is possible to achieve very high time-resolution measurements. Moreover, the high-altitude data from HAWC allows to observe the shape of the pressure anomaly with less perturbations compared to sea level detectors. Given the particular location and the detection method of HAWC, our high-altitude data provides valuable information that contributes to fully characterize this once-in-a-century phenomenon. 

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3. Study of mass composition of cosmic rays with IceTop and IceCube

   https://doi.org/10.22323/1.395.0323  

   Abbasi, Rasha ; Ackermann, Markus ; Adams, Jenni ; Aguilar, Juanan ; Ahlers, M. ; Ahrens, Maryon ; Alispach, Cyril Martin ; Alves Junior, Antonio Augusto ; Amin, Najia Moureen ; An, Rui ; et al ( July 2021 , Proceedings of the 37th International Cosmic Ray Conference)

   null (Ed.)

   The IceCube Neutrino Observatory is a multi-component detector at the South Pole which detects high-energy particles emerging from astrophysical events. These particles provide us with insights into the fundamental properties and behaviour of their sources. Besides its principal usage and merits in neutrino astronomy, using IceCube in conjunction with its surface array, IceTop, also makes it a unique three-dimensional cosmic-ray detector. This distinctive feature helps facilitate detailed cosmic-ray analysis in the transition region from galactic to extragalactic sources. We will present the progress made on multiple fronts to establish a framework for mass-estimation of primary cosmic rays. The first technique relies on a likelihood-based analysis of the surface signal distribution and improves upon the standard reconstruction technique. The second uses advanced methods in graph neural networks to use the full in-ice shower footprint, in addition to global shower-footprint features from IceTop. A comparison between the two methods for composition analysis as well as a possible extension of the analysis techniques for sub-PeV cosmic-ray air-showers will also be discussed. 

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4. Physics Potential of a Radio Surface Array at the South Pole

   https://doi.org/10.1051/epjconf/201921601007  

   Schröder, Frank G. ; Riccobene, G. ; Biagi, S. ; Capone, A. ; Distefano, C. ; Piattelli, P. ( January 2019 , EPJ Web of Conferences)

   A surface array of radio antennas will enhance the performance of the IceTop array and enable new, complementary science goals. First, the accuracy for cosmic-ray air showers will be increased since the radio array provides a calorimetric measurement of the electromagnetic component and is sensitive to the position of the shower maximum. This enhanced accuracy can be used to better measure the mass composition, to search for possible mass-dependent anisotropies in the arrival directions of cosmic rays, and for more thorough tests of hadronic interaction models. Second, the sensitivity of the radio array to inclined showers will increase the sky coverage for cosmic-ray measurements. Third, the radio array can be used to search for PeV photons from the Galactic Center. Since IceTop is planned to be enhanced by a scintillator array in the near future, a radio extension sharing the same infrastructure can be installed with minimal additional effort and excellent scientific prospects. The combination of ice-Cherenkov, scintillation, and radio detectors at IceCube will provide unprecedented accuracy for the study of highenergy Galactic cosmic rays. 

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5. Testing the Compatibility of the Depth of the Shower Maximum Measurements performed at Telescope Array and the Pierre Auger Observatory: Auger-TA Mass Composition Working Group Report

   https://doi.org/10.1051/epjconf/202328302008  

   Bergman, Douglas ; Bellido, Jose ; de Souza, Vitor ; Engel, Ralph ; Gerber, Zane ; Kim, JiHyun ; Mayotte, Eric ; Tkachenko, Olena ; Unger, Michael ; Yushkov, Alexey ( January 2023 , EPJ Web of Conferences)

   De Mitri, I. ; Barbato, F.C.T. ; Boncioli, D. ; Evoli, C. ; Pagliaroli, G. ; Salamida, F. (Ed.)

   The Telescope Array and the Pierre Auger Observatory estimate the composition of ultra-high-energy cosmic rays by observing the distribution of depths of air-shower maxima, X max . Both experiments directly observe the longitudinal development of air showers using fluorescence telescopes with surface particle detectors used in conjunction to provide precision in determining air-shower geometry. The two experiments differ in the details of the analysis of events, so a direct comparison of X max distributions is not possible. The Auger – Telescope Array Composition Working Group presents their results from a technique to compare X max measurements from Auger with those of Telescope Array. In particular, the compatibility of the first two moments of the X max distributions of Auger with the data from the Black Rock Mesa and Long Ridge detectors of the Telescope Array is tested for energies above 10 18.2 eV. Quantitative comparisons are obtained using air-shower simulations of four representative species made using the Sibyll 2.3d high-energy interaction model. These are weighted to fit the fractional composition seen in Auger data and reconstructed using the Telescope Array detector response and analysis methods. 

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