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Universe
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Ultra High Energy Photons
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Ultra High Energy Photons

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "High Energy Nuclear and Particle Physics".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 24392

Special Issue Editors

Dr. Mariangela Settimo

E-Mail
Guest Editor
SUBATECH, IMT-Atlantique, CNRS/IN2P3, Université de Nantes, 4 rue Alfred Kastler, 44300 Nantes, France
Interests: astroparticle physics; ultra-high energy photons; ultra-high energy cosmic rays; neutrino physics; dark matter; particle physics detectors
Dr. Piotr Homola

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Guest Editor
The H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Kraków, Poland
Interests: high energy astroparticle physics; cosmic rays; ultra-high energy photons, cosmic ray ensembles; cosmic ray simulations; extensive air showers; preshower effect; citizen science; discoverology; foundations of science; philosophy of science

Special Issue Information

Dear Colleagues,

Photons at ultra-high energies (UHE) are not yet observed but still very promising candidate particles of cosmic rays. In addition to their astrophysical importance, they are a smoking gun of photo−pion production interactions on the cosmic microwave background. An observation of UHE photons could contribute to solve the long-standing puzzle of UHE cosmic rays, which includes questions about the origin, chemical composition, and propagation processes on the way to Earth of the most energetic particles known. Moreover, UHE photons are expected from exotic scenarios (“top-down” models) which explain the cosmic ray origin, such as the decay of super-heavy dark matter. In addition, as proposed by some recent initiatives, energetic photons which undergo interactions with extragalactic background light and induce electromagnetic cascades might be observed indirectly as multiprimary cosmic-ray events, so-called cosmic ray ensembles, which would offer a new type of astrophysical information. Photons are thus sensitive probes of the extragalactic ambient (e.g., EBL, magnetic fields), new physics scenarios (violation of the Lorentz invariance, photon-axion conversion, etc.) and properties of the astrophysical sources of the highest energy cosmic rays.

Experimental results impose stringent constraints on the flux of UHE photons. Nevertheless, observatories worldwide are currently enhancing their sensitivity and should ultimately be able to observe ultra-high energy photons in the coming year or exclude many astrophysical scenarios which describe their origin and propagation.

This special issue aims at collecting contributions from all the subfields of astroparticle physics where connections to ultra-high energy photons might be considered, namely those related to models and predictions of ultra-high energy cosmic rays (astrophysics origin, super-heavy particles), propagation effects and new physics (e.g. Lorentz invariance violation), detection techniques, analysis approaches, and current experimental results. The perspectives for the future of research focused on ultra-high energy photons including the implications of their detection or non-detection are also to be covered.

Dr. Mariangela Settimo
Dr. Piotr Homola
Guest Editors

Manuscript Submission Information

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Keywords

  • ultra-high energy photons
  • cosmic rays
  • cosmic ray ensembles  
  • extensive air showers
  • multimessenger astroparticle physics

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Published Papers (11 papers)

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Research

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17 pages, 6970 KiB  
Article
On the Search for the Galactic PeVatrons by Means of Gamma-Ray Astronomy
by Sabrina Casanova
Universe 2022, 8(10), 505; https://doi.org/10.3390/universe8100505 - 26 Sep 2022
Cited by 6 | Viewed by 1473
Abstract
Cosmic rays are ultra-relativistic particles that slam into the atmosphere from all directions in the sky. Gamma rays emitted when cosmic rays interact with Galactic gas and radiation fields are a powerful tool to investigate their origin. Many candidate CR sources have been [...] Read more.
Cosmic rays are ultra-relativistic particles that slam into the atmosphere from all directions in the sky. Gamma rays emitted when cosmic rays interact with Galactic gas and radiation fields are a powerful tool to investigate their origin. Many candidate CR sources have been discovered in GeV-to-PeV gamma rays. However, the major contributors to the CR population, especially at the highest energies, are still unknown. We give here a state of the art report on the search for the sources of Galactic cosmic rays by means of gamma-ray astronomical methods. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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15 pages, 2261 KiB  
Article
Simulation of the Isotropic Ultra-High Energy Photon Flux in the Solar Magnetic Field
by Bożena Poncyljusz, Tomasz Bulik, Niraj Dhital, Oleksandr Sushchov, Sławomir Stuglik, Piotr Homola, David Alvarez-Castillo, Marcin Piekarczyk, Tadeusz Wibig, Jaroslaw Stasielak, Péter Kovács, Katarzyna Smelcerz, Maria Dolores Rodriguez Frias, Michał Niedźwiecki, Justyna Miszczyk, Tomasz Sośnicki, Łukasz Bibrzycki, Arman Tursunov, Luis Del Peral and Krzysztof Rzecki
Universe 2022, 8(10), 498; https://doi.org/10.3390/universe8100498 - 22 Sep 2022
Cited by 2 | Viewed by 2248
Abstract
Both the lack of observation of ultra-high energy (UHE) photons and the limitations of the state-of-the-art methodology being applied for their identification motivate studies on alternative approaches to the relevant simulations and the related observational strategies. One such new approach is proposed in [...] Read more.
Both the lack of observation of ultra-high energy (UHE) photons and the limitations of the state-of-the-art methodology being applied for their identification motivate studies on alternative approaches to the relevant simulations and the related observational strategies. One such new approach is proposed in this report and it concerns new observables allowing indirect identification of UHE photons through cosmic ray phenomena composed of many spatially correlated extensive air showers or primary cosmic rays observed at one time. The study is based on simulations of interactions of UHE photons with the magnetic field of the Sun using the PRESHOWER program with some essential modifications. One of the expected results of such interactions is a generation of cosmic ray ensembles (CREs) in the form of very thin and very elongated cascades of secondary photons of energies spanning the whole cosmic ray energy spectrum. Upon entering the Earth’s atmosphere, these cascades or their parts may generate uniquely characteristic walls of spatially correlated extensive air showers, and the effect is expected also in cases when primary UHE photons are not directed towards the Earth. Particle distributions in these multi-primary UHE photon footprints are expected to have thicknesses of the order of meters and elongations reaching even hundreds of millions of kilometers, making them potentially observable with a global, multi-experiment approach, including re-exploring of the historical data, with the expected event rate exceeding the capabilities of even very large cosmic ray observatories. In this report, we introduce for the first time the methods allowing for simulating the isotropic flux of UHE photons in the Sun’s vicinity. Presented methods were verified and optimised in such a way that they would successfully model the cumulative spatial distribution of secondary photons at the top of the atmosphere. The preliminary results of simulations for the UHE photon flux of energy 100 EeV demonstrate the possibility of simulating potentially observable quantities related to CRE induced by UHE photons: densities, energy spectra and geographical orientations of secondary particles at the top of the Earth’s atmosphere. A measurement of at least one of these quantities would be equivalent to a confirmation of the existence of UHE photons, which would give an insight into fundamental physics processes at unprecedentedly high energies, far beyond the reach of man-made accelerators. On the other hand, a lack of such an observation would allow for further constraining of these fundamental processes with the physically new upper limits on UHE photon fluxes after careful analysis of the technical observation ability. The novel advantage of such an approach would lay in the purely electrodynamical character of the underlying simulations which are fully independent on extrapolations of hadronic interaction models by many orders of magnitude. Such extrapolations are necessary in the UHE photon identification methods based on the analyses of properties of individual extensive air showers presently used to determine the UHE photon upper limits. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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20 pages, 1347 KiB  
Article
Analysis of the Capability of Detection of Extensive Air Showers by Simple Scintillator Detectors
by Jerzy Seweryn Pryga, Weronika Stanek, Krzysztof Wiesław Woźniak, Piotr Homola, Kevin Almeida Cheminant, Sławomir Stuglik, David Alvarez-Castillo, Łukasz Bibrzycki, Marcin Piekarczyk, Olaf Bar, Tadeusz Wibig, Arman Tursunov, Michał Niedźwiecki, Tomasz Sośnicki and Krzysztof Rzecki
Universe 2022, 8(8), 425; https://doi.org/10.3390/universe8080425 - 18 Aug 2022
Cited by 2 | Viewed by 1983
Abstract
One of the main objectives of the CREDO project is to register cosmic-ray cascades in many distributed detectors in the search for so-called Cosmic-Ray Ensembles (CRE). This requires precise knowledge of the probability of detection of individual Extensive Air Showers (EAS) in a [...] Read more.
One of the main objectives of the CREDO project is to register cosmic-ray cascades in many distributed detectors in the search for so-called Cosmic-Ray Ensembles (CRE). This requires precise knowledge of the probability of detection of individual Extensive Air Showers (EAS) in a very wide range of energies and an analysis of their correlations. The standard approach based on detailed and extensive simulations is not possible for many such systems; thus, a faster method is developed. Knowing the characteristics of EAS from more general simulations, any required probability is calculated. Such probability depends on particle density at a given point, which is a function of the distance from the centre of the cascade, the energy, mass and the zenith angle of the primary cosmic-ray particle. It is necessary to use proper distribution of the number of secondary particles reaching the ground and their fluctuations. Finally, to calculate the total probability of EAS detection, the primary cosmic-ray spectrum and abundance of various particles in it have to be taken into account. The effective probability can be used to estimate the expected number of EAS events measured by a set of small detectors. In this work, results from several versions of calculations, with different complexity levels, are presented and compared with the first measurement performed with a test detector system. These results confirm that the majority of events observed with this small detector array are caused by cosmic-ray particles with very high energies. Such analysis can be also useful for the design of more effective systems in the future. Slightly larger systems of simple detectors may be used to distinguish cascades initiated by photons from those started from other primary cosmic-ray particles. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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19 pages, 388 KiB  
Article
On the Issue of Magnetic Monopoles in the Prospect of UHE Photon Searches
by Łukasz Bratek and Joanna Jałocha
Universe 2022, 8(8), 422; https://doi.org/10.3390/universe8080422 - 15 Aug 2022
Cited by 1 | Viewed by 1323
Abstract
Ultra-high energy (UHE) photons with energies exceeding 1018eV can potentially be observed. They are produced in various processes involving electrically charged particles. However, more exotic scenarios are also possible. UHE photons could be emitted in encounters of massive magnetically charged monopole-antimonopole [...] Read more.
Ultra-high energy (UHE) photons with energies exceeding 1018eV can potentially be observed. They are produced in various processes involving electrically charged particles. However, more exotic scenarios are also possible. UHE photons could be emitted in encounters of massive magnetically charged monopole-antimonopole pairs or in processes associated with monopoles accelerated to high energies, typically 1021eV or beyond. Observing UHE photons can pose constraints on the properties of magnetic monopoles. There are compelling theoretical reasons in favor of the presence of magnetic monopoles in nature. The predicted observational signatures of these particles are therefore searched for in dedicated experiments currently in operation. Despite these attempts, magnetic monopoles have yet to be empirically proved. There are also theoretical reasons why magnetic monopoles allowed by Dirac’s theory might not be realized in nature in the form of isolated particles. Detection or non-detection of UHE photon signatures of magnetic monopoles would bring us closer to solving this fascinating puzzle. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
11 pages, 496 KiB  
Article
Upper Limit on the Diffuse Radio Background from GZK Photon Observation
by Graciela B. Gelmini, Oleg Kalashev and Dmitri Semikoz
Universe 2022, 8(8), 402; https://doi.org/10.3390/universe8080402 - 31 Jul 2022
Cited by 7 | Viewed by 1559
Abstract
Here, we point out that an observation of ultrahigh energy cosmic ray (UHECR) photons, “GZK photons”, could provide an upper limit on the level of the extragalactic radio background, depending on the level of UHECR proton primaries (to be determined after a few [...] Read more.
Here, we point out that an observation of ultrahigh energy cosmic ray (UHECR) photons, “GZK photons”, could provide an upper limit on the level of the extragalactic radio background, depending on the level of UHECR proton primaries (to be determined after a few years of data taking by the Pierre Auger Observatory upgrade AugerPrime). We also update our 2005 prediction of the range of GZK photon fluxes expected from proton primaries. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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11 pages, 741 KiB  
Article
Probing Spacetime Foam with Extragalactic Sources of High-Energy Photons
by Y. Jack Ng and Eric S. Perlman
Universe 2022, 8(7), 382; https://doi.org/10.3390/universe8070382 - 19 Jul 2022
Cited by 4 | Viewed by 1505
Abstract
Quantum fluctuations can endow spacetime with a foamy structure. In this review article, we discuss our various proposals to observationally constrain models of spacetime foam. One way is to examine if the light wave-front from a distant quasar or GRB can be noticeably [...] Read more.
Quantum fluctuations can endow spacetime with a foamy structure. In this review article, we discuss our various proposals to observationally constrain models of spacetime foam. One way is to examine if the light wave-front from a distant quasar or GRB can be noticeably distorted by spacetime-foam-induced phase incoherence. As the phase fluctuations are proportional to the distance to the source but inversely proportional to the wavelength, ultra-high energy photons (>1 TeV) from distant sources are particularly useful. We elaborate on several proposals, including the possibility of detecting spacetime foam by observing “seeing disks” in the images of distant quasars and active galactic nuclei. We also discuss the appropriate distance measure for calculating the expected angular broadening. In addition, we discuss our more recent work in which we investigate whether wave-front distortions on small scales (due to spacetime foam) can cause distant objects become undetectable because the phase fluctuations have accumulated to the point at which image formation is impossible. Another possibility that has recently become accessible is to use interferometers to observe cosmologically distant sources, thereby giving a large baseline perpendicular to the local wave vector over which the wave front could become corrugated and thus distorted, reducing or eliminating its fringe visibility. We argue that all these methods ultimately depend on the availability of ways (if any) to carry out proper averaging of contributions from different light paths from the source to the telescope. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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Review

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20 pages, 2415 KiB  
Review
Searches for Ultra-High-Energy Photons at the Pierre Auger Observatory
by The Pierre Auger Collaboration
Universe 2022, 8(11), 579; https://doi.org/10.3390/universe8110579 - 2 Nov 2022
Cited by 8 | Viewed by 3254
Abstract
The Pierre Auger Observatory, which is the largest air-shower experiment in the world, offers unprecedented exposure to neutral particles at the highest energies. Since the start of data collection more than 18 years ago, various searches for ultra-high-energy (UHE, [...] Read more.
The Pierre Auger Observatory, which is the largest air-shower experiment in the world, offers unprecedented exposure to neutral particles at the highest energies. Since the start of data collection more than 18 years ago, various searches for ultra-high-energy (UHE, E≳1017eV) photons have been performed, either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with transient events such as gravitational wave events. In the present paper, we summarize these searches and review the current results obtained using the wealth of data collected by the Pierre Auger Observatory. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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8 pages, 268 KiB  
Review
Blazar Jets as Possible Sources of Ultra-High Energy Photons: A Short Review
by Gopal Bhatta
Universe 2022, 8(10), 513; https://doi.org/10.3390/universe8100513 - 1 Oct 2022
Cited by 5 | Viewed by 1662
Abstract
In this paper, I present a qualitative discussion on the prospect of production of ultra-high photons in blazars. The sources are a subclass of active galactic nuclei which host supermassive black holes and fire relativistic jets into the intergalactic medium. The kpc-scale jets [...] Read more.
In this paper, I present a qualitative discussion on the prospect of production of ultra-high photons in blazars. The sources are a subclass of active galactic nuclei which host supermassive black holes and fire relativistic jets into the intergalactic medium. The kpc-scale jets are believed to be dominated by Poynting flux and constitute one of the most efficient cosmic particle accelerators, that potentially are capable of accelerating the particles up to EeV energies. Recent IceCube detection of astrophysical neutrino emissions, in coincidence with the enhanced gamma-ray from Tev blazar TXS 0506 + 056, further supports hadronic models of blazar emissions in which particle acceleration processes, such as relativistic shocks, magnetic re-connection, and relativistic turbulence, could energize hadrons, e.g., protons, up to energies equivalent to billions of Lorentz factors. The ensuing photo-pionic processes may then result in gamma-rays accompanied by neutrino flux. Furthermore, the fact that blazars are the dominant source of observed TeV emission encourages search for signatures of acceleration scenarios that would lead to the creation of ultra-high-energy photons. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
16 pages, 532 KiB  
Review
Ultra-High-Energy Astroparticles as Probes for Lorentz Invariance Violation
by Rodrigo Guedes Lang, Humberto Martínez-Huerta and Vitor de Souza
Universe 2022, 8(8), 435; https://doi.org/10.3390/universe8080435 - 22 Aug 2022
Cited by 1 | Viewed by 1784
Abstract
Compelling evidence for Lorentz invariance violation (LIV) would demand a complete revision of modern physics. Therefore, searching for a signal or extending the validity of the invariance is fundamental for building our understanding of the extreme phenomena in the Universe. In this paper, [...] Read more.
Compelling evidence for Lorentz invariance violation (LIV) would demand a complete revision of modern physics. Therefore, searching for a signal or extending the validity of the invariance is fundamental for building our understanding of the extreme phenomena in the Universe. In this paper, we review the potential of ultra-high-energy astroparticles in setting limits on LIV. The standard framework of LIV studies in astroparticle physics is reviewed and its use on the electromagnetic and hadronic sectors are discussed. In particular, the current status of LIV tests using experimental data on ultra-high-energy photons and cosmic rays is addressed. A detailed discussion with improved argumentation about the LIV kinematics of the relevant interactions is shown. The main previous results are presented together with new calculations based on recently published astrophysical models. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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31 pages, 464 KiB  
Review
Lorentz Symmetry Violation of Cosmic Photons
by Ping He and Bo-Qiang Ma
Universe 2022, 8(6), 323; https://doi.org/10.3390/universe8060323 - 9 Jun 2022
Cited by 23 | Viewed by 2993
Abstract
As a basic symmetry of space-time, Lorentz symmetry has played important roles in various fields of physics, and it is a glamorous question whether Lorentz symmetry breaks. Since Einstein proposed special relativity, Lorentz symmetry has withstood very strict tests, but there are still [...] Read more.
As a basic symmetry of space-time, Lorentz symmetry has played important roles in various fields of physics, and it is a glamorous question whether Lorentz symmetry breaks. Since Einstein proposed special relativity, Lorentz symmetry has withstood very strict tests, but there are still motivations for Lorentz symmetry violation (LV) research from both theoretical consideration and experimental feasibility, that attract physicists to work on LV theories, phenomena and experimental tests with enthusiasm. There are many theoretical models including LV effects, and different theoretical models predict different LV phenomena, from which we can verify or constrain LV effects. Here, we introduce three types of LV theories: quantum gravity theory, space-time structure theory and effective field theory with extra-terms. Limited by the energy of particles, the experimental tests of LV are very difficult; however, due to the high energy and long propagation distance, high-energy particles from astronomical sources can be used for LV phenomenological researches. Especially with cosmic photons, various astronomical observations provide rich data from which one can obtain various constraints for LV researches. Here, we review four common astronomical phenomena which are ideal for LV studies, together with current constraints on LV effects of photons. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
15 pages, 352 KiB  
Review
Testing Quantum Gravity in the Multi-Messenger Astronomy Era
by Aleksandra Piórkowska-Kurpas and Marek Biesiada
Universe 2022, 8(6), 321; https://doi.org/10.3390/universe8060321 - 8 Jun 2022
Cited by 2 | Viewed by 2001
Abstract
Quantum gravity (QG) remains elusive despite almost century-long efforts to combine general relativity and quantum mechanics. All the approaches triggered and powered by purely theoretical considerations eventually failed with a prevailing feeling of a complete lack of guidance from the experimental side. Currently, [...] Read more.
Quantum gravity (QG) remains elusive despite almost century-long efforts to combine general relativity and quantum mechanics. All the approaches triggered and powered by purely theoretical considerations eventually failed with a prevailing feeling of a complete lack of guidance from the experimental side. Currently, however, this circumstance is beginning to change considerably. We have entered the era of multi-messenger astronomy. The electromagnetic window to the universe—so far the only one—has been tremendously enlarged in the energy range beyond gamma rays up to ultra-high-energy photons and has been complemented by other messengers: high-energy cosmic rays, cosmic neutrinos, and gravitational waves (GWs). This has created a unique environment in which to observationally constrain various phenomenological QG effects. In this paper, we focus on the LIV phenomenology manifested as energy-dependent time-of-flight delays and strong lensing time delays. We review results regarding time-of-flight delays obtained with GRBs. We also recall the idea of energy-dependent lensing time delays, which allow one to constrain LIV models independently of the intrinsic time delay. Lastly, we show how strongly a gravitationally lensed GW signal would place interesting constraints on the LIV. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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