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Register a new userHigh energy electromagnetic cascades in extragalactic space: physics and features
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Using the analytic modeling of the electromagnetic cascades compared with more precise numerical simulations we describe the physical properties of electromagnetic cascades developing in the universe on CMB and EBL background radiations. A cascade is initiated by very high energy photon or electron and the remnant photons at large distance have two-component energy spectrum, $propto E^{-2}$ ($propto E^{-1.9}$ in numerical simulations) produced at cascade multiplication stage, and $propto E^{-3/2}$ from Inverse Compton electron cooling at low energies. The most noticeable property of the cascade spectrum in analytic modeling is strong universality, which includes the standard energy spectrum and the energy density of the cascade $omega_{rm cas}$ as its only numerical parameter. Using numerical simulations of the cascade spectrum and comparing it with recent Fermi LAT spectrum we obtained the upper limit on $omega_{rm cas}$ stronger than in previous works. The new feature of the analysis is $E_{max}$ rule. We investigate the dependence of $omega_{rm cas}$ on the distribution of sources, distinguishing two cases of universality: the strong and weak ones.
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Atmospheric muons are one of the main backgrounds for current Water- and Ice-Cherenkov neutrino telescopes designed to detect astrophysical neutrinos. The inclusive fluxes of atmospheric muons and neutrinos from hadronic interactions of cosmic rays have been extensively studied with Monte Carlo and cascade equation methods, for example, CORSIKA and MCEq. However, the muons that are pair produced in electromagnetic interaction of high energy photons are quantitatively not well understood. We present new simulation results and assess the model dependencies of the high-energy atmospheric muon flux including those from electromagnetic interactions, using a new numerical electromagnetic cascade equation solver EmCa that can be easily coupled with the hadronic solver MCEq. Both codes are in active development with the particular aim to become part of the next generation CORSIKA 8 air shower simulation package. The combination of EmCa and MCEq accounts for material effects that have not been previously included in most of the available codes. Hence, the influence of these effects on the air showers will also be briefly discussed.
Electromagnetic-Cascades (EmCa) is a Python package for the simulation of electromagnetic cascades in various materials. The showers are modeled using cascade equations and the relevant interactions, specifically pair production, Bremsstrahlung, Compton scattering and ionization. This methodology has the advantage of being computationally inexpensive and fast, unlike Monte Carlo methods. The code includes low and high energy material effects, allowing for a high range of validity of the simulation results. EmCa is easily extendable and offers a framework for testing different electromagnetic interaction models. In combination with MCEq, a Python package for hadronic particle showers using cascade equations, full simulations of atmospheric fluxes can be done.
We present a procedure for reconstructing particle cascades from event data measured in a high energy physics experiment. For evaluating the hypothesis of a specific physics process causing the observed data, all possible reconstructi
TeV photons from extragalactic sources are absorbed in the intergalactic medium and initiate electromagnetic cascades. These cascades offer a unique tool to probe the properties of the universe at cosmological scales. We present a new Monte Carlo code dedicated to the physics of such cascades. This code has been tested against both published results and analytical approximations, and is made publicly available. Using this numerical tool, we investigate the main cascade properties (spectrum, halo extension, time delays), and study in detail their dependence on the physical parameters (extra-galactic magnetic field, extra-galactic background light, source redshift, source spectrum and beaming emission). The limitations of analytical solutions are emphasised. In particular, analytical approximations account only for the first generation of photons and higher branches of the cascade tree are neglected.
We report the observation of radar echoes from the ionization trails of high-energy particle cascades. These data were taken at the SLAC National Accelerator Laboratory, where the full electron beam ($sim$10$^9$ e$^-$ at $sim$10 GeV/e$^-$) was directed into a plastic target to simulate an ultra high-energy neutrino interaction. This target was interrogated with radio waves, and coherent radio reflections from the cascades were detected, with properties consistent with theoretical expectations. This is the first definitive observation of radar echoes from high-energy particle cascades, which may lead to a viable neutrino detection technology for energies $gtrsim 10^{16}$ eV.
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