Abstract High-energy photons can produce electron–positron pairs upon interacting with the extragalactic background light. These pairs will in turn be deflected by the intergalactic magnetic field ...(IGMF), before possibly up-scattering photons of the cosmic microwave background, thereby initiating an electromagnetic cascade. The nonobservation of an excess of GeV photons and an extended halo around individual blazars due to this electromagnetic cascade can be used to constrain the properties of the IGMF. In this work, we use publicly available data of 1ES 0229+200 obtained with the Fermi Large Area Telescope and the High Energy Stereoscopic System to constrain cosmological MHD simulations of various magnetogenesis scenarios, and find that all models without a strong space-filling primordial component or overoptimistic dynamo amplifications can be excluded at the 95% confidence level. In fact, we find that the fraction of space filled by a strong IGMF has to be at least f ≳ 0.67, thus excluding most astrophysical production scenarios. Moreover, we set lower limits of B 0 > 5.1 × 10 −15 G ( B 0 > 1.0 × 10 −14 G) for a space-filling primordial IGMF for a blazar activity time of Δ t = 10 4 yr (Δ t = 10 7 yr).
Detecting ALP wiggles at TeV energies Kachelrieß, M.; Tjemsland, J.
Journal of cosmology and astroparticle physics,
01/2024, Letnik:
2024, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Axions and axion-like-particles (ALPs) are characterised by their two-photon
coupling, which entails so-called photon-ALP oscillations as photons
propagate through a magnetic field. These ...oscillations lead
to distinctive signatures in the energy spectrum of high-energy photons
from astrophysical sources, allowing one to probe the existence of ALPs.
In particular, photon-ALP oscillations will induce energy dependent
oscillatory features, or “ALP wiggles”, in the photon spectra. We propose
to use the discrete power spectrum to search for ALP wiggles and
present a model-independent statistical test.
By using PKS 2155-304 as an example, we show that the method has the
potential to significantly improve the experimental sensitivities for ALP
wiggles, and that the ALP wiggles
may be detected using the Cherenkov Telescope Array (CTA)
for optimistic values of the photon-ALP coupling constant and the magnetic
field.
Moreover, we discuss how these sensitivities depend on the modelling of the
magnetic field. We find
that the use of realistic magnetic field models, due to their larger cosmic
variance, substantially enhances detection prospects compared to the use of
simplified models.
Abstract
Photons propagating in an external magnetic field may oscillate into
axions or axion-like particles (ALPs). Such oscillations will lead to
characteristic features in the energy spectrum of ...high-energy photons from
astrophysical sources that can be used to probe the existence of ALPs.
In this work, we revisit
the signatures of these oscillations and stress the importance of a proper
treatment of turbulent magnetic fields.
We implement axions into
ELMAG
,
a standard tool for modelling in a Monte Carlo framework the propagation
of gamma-rays in the Universe, complementing thereby
the usual description of photon-axion oscillations with a Monte Carlo
treatment of high-energy photon propagation and interactions.
We also propose an alternative method of detecting axions through
the discrete power spectrum using as observable
the energy dependence of wiggles in the photon spectra.
Antideuteron and antihelium nuclei have been proposed as a detection channel for dark matter annihilations and decays in the Milky Way, due to the low astrophysical background expected. To estimate ...both the signal for various dark matter models and the astrophysical background, one usually employs the coalescence model in a Monte Carlo framework. This allows one to treat the production of antinuclei on an event-by-event basis, thereby taking into account momentum correlations between the antinucleons involved in the process. This approach lacks, however, an underlying microscopic picture, and the numerical value of the coalescence parameter obtained from fits to different reactions varies considerably. Here we propose instead to combine event-by-event Monte Carlo simulations with a microscopic coalescence picture based on the Wigner function representations of the produced antinuclei states. This approach allows us to include in a semi-classical picture both the size of the formation region, which is process dependent, and the momentum correlations. The model contains a single, universal parameter which is fixed by fitting the production spectra of antideuterons in proton–proton interactions, measured at the Large Hadron Collider. Using this value, the model describes well the production of various antinuclei both in electron–positron annihilation and in proton–proton collisions.
The formation of light nuclei can be described as the coalescence of clusters of nucleons into nuclei. In the case of small interacting systems, such as dark matter and
e
+
e
-
annihilations or
pp
...collisions, the coalescence condition is often imposed only in momentum space and hence the size of the interaction region is neglected. On the other hand, in most coalescence models used for heavy ion collisions, the coalescence probability is controlled mainly by the size of the interaction region, while two-nucleon momentum correlations are either neglected or treated as collective flow. Recent experimental data from
pp
collisions at LHC have been interpreted as evidence for such collective behaviour, even in small interacting systems. We argue that these data are naturally explained in the framework of conventional QCD inspired event generators when both two-nucleon momentum correlations and the size of the hadronic emission volume are taken into account. To include both effects, we employ a per-event coalescence model based on the Wigner function representation of the produced nuclei states. This model reproduces well the source size for baryon emission and the coalescence factor
B
2
measured recently by the ALICE collaboration in
pp
collisions.
Antideuteron and antihelium nuclei have been proposed as promising detection channels for dark matter because of the low astrophysical backgrounds expected. To estimate both potential exotic ...contributions and their backgrounds, one usually employs the coalescence model in momentum space. Here we use instead a newly developed coalescence model based on the Wigner function representations of the produced nuclei states. This approach includes both the process-dependent size of the formation region of antinuclei, and the momentum correlations of coalescing antinucleons in a semi-classical picture. The model contains a single universal parameter σ that we tune to experimental data on antideuteron production in electron-positron, proton-proton and proton-nucleus collisions. The obtained value σ≃1 fm agrees well with its physical interpretation as the size of the formation region of antinuclei in collisions of point-like particles. This model allows us therefore to calculate in a consistent frame-work the antideuteron and antihelium fluxes both from secondary production and from dark matter annihilations. We find that the antihelium-3 flux falls short by more than an order of magnitude of the detection sensitivity of the AMS-02 experiment, assuming standard cosmic ray propagation parameters, while the antideuteron flux can be comparable to the sensitivities of the AMS-02 and GAPS experiments.
The precise measurement of cosmic-ray antinuclei serves as an important means for identifying the nature of dark matter and other new astrophysical phenomena, and could be used with other cosmic-ray ...species to understand cosmic-ray production and propagation in the Galaxy. For instance, low-energy antideuterons would provide a “smoking gun” signature of dark matter annihilation or decay, essentially free of astrophysical background. Studies in recent years have emphasized that models for cosmic-ray antideuterons must be considered together with the abundant cosmic antiprotons and any potential observation of antihelium. Therefore, a second dedicated Antideuteron Workshop was organized at UCLA in March 2019, bringing together a community of theorists and experimentalists to review the status of current observations of cosmic-ray antinuclei, the theoretical work towards understanding these signatures, and the potential of upcoming measurements to illuminate ongoing controversies. This review aims to synthesize this recent work and present implications for the upcoming decade of antinuclei observations and searches. This includes discussion of a possible dark matter signature in the AMS-02 antiproton spectrum, the most recent limits from BESS Polar-II on the cosmic antideuteron flux, and reports of candidate antihelium events by AMS-02; recent collider and cosmic-ray measurements relevant for antinuclei production models; the state of cosmic-ray transport models in light of AMS-02 and Voyager data; and the prospects for upcoming experiments, such as GAPS. This provides a roadmap for progress on cosmic antinuclei signatures of dark matter in the coming years.
Decays of mesons produced in cosmic ray induced air showers in Earth’s atmosphere can lead to a flux of light exotic particles which can be detected in underground experiments. We evaluate the energy ...spectra of the light neutral mesons π0, η, ρ0, ω, ϕ and J∕ψ produced in interactions of cosmic ray protons and helium nuclei with air using QCD inspired event generators. Summing up the mesons produced in the individual hadronic interactions of air showers, we obtain the resulting fluxes of undecayed mesons. As an application, we re-consider the case of millicharged particles created in the electromagnetic decay channels of neutral mesons.
Axions and axion-like-particles (ALPs) are well motivated beyond the standard model particles that can explain a variety of unsolved problems in physics, such as the strong CP problem and the nature ...of dark matter. These particles are characterised by their two-photon coupling, which leads to so-called photon-ALP oscillation as photons propagate through an external magnetic field. Such oscillations lead to characteristic signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing us to probe the existence of ALPs and possibly dark matter. We review the signatures from ALPs in photon spectra and discuss a new method that can be used to directly search for the energy dependence of the oscillations. The focus is on photons at TeV-energies relevant for the upcoming Cherenkov Telescope Array (CTA).
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