We compare two techniques for simulation of the propagation of ultra-high-energy cosmic rays (UHECR) in intergalactic space: the Monte Carlo approach and a method based on solving transport equations ...in one dimension. For the former, we adopt the publicly available tool CRPropa and for the latter, we use the code TransportCR, which has been developed by the first author and used in a number of applications, and is made available online with publishing this paper. While the CRPropa code is more universal, the transport equation solver has the advantage of a roughly 100 times higher calculation speed. We conclude that the methods give practically identical results for proton or neutron primaries if some accuracy improvements are introduced to the CRPropa code.
We examine the role of the large-scale anisotropy of the high-energy cosmic ray distribution in a search for the heavy decaying dark matter (DM) signal. Using recent anisotropy measurements from the ...extensive air shower (EAS) observatories, we constrain the lifetime of the DM particles with masses 10
7
≤
M
X
≤ 10
16
GeV. These constraints appear to be weaker than that obtained with the high-energy gamma-ray limits. We also estimate the desired precision level for the anisotropy measurements to discern the decaying DM signal marginally allowed by the gamma-ray limits and discuss the prospects of the DM search with the modern EAS facilities.
This study focuses on the reconstruction of neutrino direction in the Baikal-GVD experiment using convolutional neural networks and graph neural networks. Monte Carlo simulation data are utilized, ...examining single-cluster events of atmospheric neutrinos with energies ranging from 10 GeV to 100 TeV. The performance of the proposed models is evaluated against the standard reconstruction algorithm by comparing their median angular resolutions. The results show that neural networks offer enhanced accuracy over the standard algorithm, particularly, in small polar angles.
The current situation in cosmology and particle physics, which are two closely related fields of fundamental physics, is unique. The Standard Model of particle physics excellently reproduces all ...existing experimental data except for neutrino oscillations. Similarly, the comparison of the standard cosmological model with astronomical observations indicates that we well understand the evolution of the Universe from its “birth” to the present. However, to understand mechanisms of numerous cosmological phenomena, it is certainly necessary to go beyond the Standard Model. These are primarily the problems of dark matter and dark energy, generation of the baryon asymmetry of the Universe, and the mechanism of inflation expansion. The problem of the appearance of cosmic magnetic fields and the recent problem of the existence of massive black holes whose number in the Universe is much larger than the expected values are among less known, but also very important problems in conventional cosmology and astrophysics. To understand and possibly solve these problems, it is very important to provide deep insight into the Universe and to obtain data on physical processes at the early stages of the cosmological evolution. Multi-messenger observations involving all possible messengers (“windows”) provide a powerful tool for this. In addition to conventional detection of electromagnetic radiation in all bands and all types of cosmic rays, the observations of gravitational waves have recently opened a new window. A complex analysis of information obtained from various astronomical data has been performed in our works supported by the Russian Science Foundation (project no. 20-42-09010 “Opening of New Windows to the Early Universe by Means of Multi-Messenger Astronomy”). In particular, the characteristics of cosmic magnetic fields and possible mechanisms of their appearance have been studied and the observed manifestations of primary black holes have been examined using the data on gravitational waves observed at the LIGO/Virgo/KAGRA interferometers.
The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible. For this reason all current and planned UHECR experiments ...detect cosmic rays indirectly by observing the extensive air showers (EAS) initiated by cosmic ray particles in the atmosphere. The world largest statistics of the ultra-high energy EAS events is recorded by the networks of surface stations. In this paper we consider a novel approach for reconstruction of the arrival direction of the primary particle based on the deep convolutional neural network. The latter is using raw time-resolved signals of the set of the adjacent trigger stations as an input. The Telescope Array (TA) Surface Detector (SD) is an array of 507 stations, each containing two layers plastic scintillator with an area of 3 m2. The training of the model is performed with the Monte-Carlo dataset. It is shown that within the Monte-Carlo simulations, the new approach yields better resolution than the traditional reconstruction method based on the fitting of the EAS front. The details of the network architecture and its optimization for this particular task are discussed.
GZK photons as ultra-high-energy cosmic rays Gelmini, G. B.; Kalashev, O. E.; Semikoz, D. V.
Journal of experimental and theoretical physics,
06/2008, Letnik:
106, Številka:
6
Journal Article
Recenzirano
We calculate the flux of “GZK photons,” namely, the flux of ultra-high-energy cosmic rays (UHECRs) consisting of photons produced by extragalactic nucleons through the resonant photoproduction of ...pions, the so-called GZK effect. We show that for primary nucleons, the GZK-photon fraction of the total UHECR flux is between 10
−4
and 10
–2
above 10
19
eV and up to the order of 0.1 above 10
20
eV. The GZK-photon flux depends on the assumed UHECR spectrum, the slope of the nucleon flux at the source, and the distribution of sources and intervening backgrounds. Detection of this photon flux would open the way for UHECR gamma-ray astronomy. Detection of a larger photon flux would imply the emission of photons at the source or new physics. We compare the photon fractions expected for GZK photons and the minimal fractions predicted by top-down models. We find that the photon fraction above 10
19
eV is a crucial test for top-down models.
The origin and nature of ultrahigh-energy cosmic rays (UHECRs,
E
> 10
18
eV) is one of the most intriguing unsolved problems of modern astrophysics. This review is dedicated to the current status of ...research in this field. We describe the largest ongoing experiments carried out at the Pierre Auger Observatory and Telescope Array, at the first orbital detector of UHECRs, that is, TUS, and for the KLPVE and JEM-EUSO orbital telescopes, which are currently being developed. We discuss the latest results on the energy spectrum and mass composition of UHECRs and the relationship between UHECRs on the one hand and ultrahigh-energy neutrinos and photons on the other. Finally, we review the latest results on the anisotropy of the arrival directions of UHECRs, which is a crucially important area of research in the search for astrophysical sources of cosmic rays in the highest energy range.
Models of the origin of astrophysical neutrinos with energies from TeVs to PeVs are strongly constrained by multimessenger observations and population studies. Recent results point to statistically ...significant associations between these neutrinos and active galactic nuclei (AGN) selected by their radio flux observed with very-long-baseline interferometry (VLBI). This suggests that the neutrinos are produced in central parsecs of blazars, AGN with relativistic jets pointing to the observer. However, conventional AGN models tend to explain only the highest-energy part of the neutrino flux observationally associated with blazars. Here we discuss in detail how the neutrinos can be produced in the part of an AGN giving the dominant contribution to the VLBI radio flux, the radio core located close to the jet base. Physical conditions there differ both from the immediate environment of the central black hole and from the plasma blobs moving along the jet. Required neutrino fluxes, considerably smaller than those of photons, can be produced in interactions of relativistic protons, accelerated closer to the black hole, with radiation in the core.
We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). The TALE air FD 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 ∼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 describe the detector, explain the technique, and present results from a measurement of the spectrum using ∼1000 hr of observation. The observed spectrum shows a clear steepening near 1017.1 eV, along with an ankle-like structure at 1016.2 eV. These features present important constraints on the origin of galactic cosmic rays and on propagation models. The feature at 1017.1 eV may also mark the end of the galactic cosmic ray flux and the start of the transition to extragalactic sources.
Using the CompHEP package, we provide a detailed estimate of the influence of double
e
+
e
−
pair production (DPP) by photons on the propagation of ultra-high-energy electromagnetic cascades. We show ...that in the models where the cosmic ray photon energy reaches a few 10
3
EeV, a refined DPP analysis may lead to a substantial difference in the predicted photon spectrum compared to the previous rough estimates.
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