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).
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.
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.
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