High-energy cosmic rays are observed indirectly by detecting the extensive air showers initiated in Earth’s atmosphere. The interpretation of these observations relies on accurate models of air ...shower physics, which is a challenge and an opportunity to test QCD under extreme conditions. Air showers are hadronic cascades, which give rise to a muon component through hadron decays. The muon number is a key observable to infer the mass composition of cosmic rays. Air shower simulations with state-of-the-art QCD models show a significant muon deficit with respect to measurements; this is called the Muon Puzzle. By eliminating other possibilities, we conclude that the most plausible cause for the muon discrepancy is a deviation in the composition of secondary particles produced in high-energy hadronic interactions from current model predictions. The muon discrepancy starts at the TeV scale, which suggests that this deviation is observable at the Large Hadron Collider. An enhancement of strangeness production has been observed at the LHC in high-density events, which can potentially explain the puzzle, but the impact of the effect on forward produced hadrons needs further study, in particular with future data from oxygen beam collisions.
Charmed Galaxies Becker Tjus, Julia; Rhode, Wolfgang
EPJ Web of Conferences,
2023, Volume:
290
Journal Article, Conference Proceeding
Peer reviewed
Open access
The quest for finding the origins of cosmic rays has been going on for many decades. Cosmic rays as charged particles react to cosmic magnetic fields and typically travel in diffusive motion through ...the Universe. Their imprint on Earth therefore holds little information on their origin, and finding the sources of cosmic rays is a major challenge. The question of their origins has been a leading questions in physics and astrophysics in the past decades. To solve this riddle, a multimessenger approach is used, including cosmic-ray interaction products in the searches, specifically gamma-rays and neutrinos produced in the resulting particle showers. In this multimessenger picture, the detection of high-energy neutrinos from the cosmos by IceCube - as a unique tracer of cosmic rays - is an important piece of the puzzle. First evidence for neutrino emission from the active galaxies TXS0506+056 and NGC1068 indicates that a significant fraction comes from such sources. In this paper, the intriguing fact that gamma-rays seem to be absorbed in these sources discussed. The possibility of neutrinos being produced in regions of high photon or gas densities, together with the possibility of in the future revealing neutrinos from the decay of charmed particles, will be investigated, possibly opening a window to
Charmed Galaxies
.
Aims.
Radio-to-TeV observations of the bright nearby (
z
= 0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used to study the emission mechanisms in its ...relativistic jet.
Methods.
We examined the multi-wavelength variability and the correlations of the light curves obtained by eight different instruments, including the First G-APD Cherenkov Telescope (FACT), observing Mrk 501 in very high-energy (VHE) gamma-rays at TeV energies. We identified individual TeV and X-ray flares and found a sub-day lag between variability in these two bands.
Results.
Simultaneous TeV and X-ray variations with almost zero lag are consistent with synchrotron self-Compton (SSC) emission, where TeV photons are produced through inverse Compton scattering. The characteristic time interval of 5−25 days between TeV flares is consistent with them being driven by Lense-Thirring precession.
Volume 2 covers knowledge discovery in particle and astroparticle physics. Instruments gather petabytes of data and machine learning is used to process the vast amounts of data and to detect relevant ...examples efficiently. The physical knowledge is encoded in simulations used to train the machine learning models. The interpretation of the learned models serves to expand the physical knowledge resulting in a cycle of theory enhancement.
Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features ...is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample.
With very high energy (VHE) gamma-ray astronomy becoming a mature branch of observational astrophysics, and the multi-messenger sky being opened up by neutrino observatories and gravitational wave ...detectors, we here propose to set up a ring of imaging air Cherenkov telescopes – the Cherenkov Telescope Ring (CTR). The aim of this proposed project would be to facilitate continuous monitoring of sources on the VHE- and multi-messenger sky with minimal time delays and with high sensitivity. Development time and construction cost could be kept comparatively low by both including existing facilities into the monitoring effort, and by relying on substantial previous expertise gained in the community on the road towards the Cherenkov Telescope Array (CTA). This way, the Ring could prove to be a highly efficient facility greatly enhancing the science prospects for future ground-based high-energy astrophysics.
Atmospheric monitoring is a field of special importance for astroparticle physics, especially for Imaging Atmospheric Cherenkov Telescopes (IACTs) as clouds will absorb and scatter the Cherenkov ...photons of air showers. Conventional tools used for atmospheric monitoring (e.g. LIDAR) are very expensive and monitor only a small part of the sky at once. Therefore, they are not suitable to perform a wide scan of the sky which is necessary to detect clouds in advance. This article gives a short overview about a method that uses an all sky camera with a 180 ° field of view to identify the cloud distribution by measuring the absorption of star light. It can be used to assign a sky quality rating to single spots, arbitrary regions or the whole sky at once within a 1 min exposure time. A cloud map can be created from the available data that can be used to determine shape and dimension of clouds and to predict their movement. The resulting data can be used by a scheduling algorithm or the operating crew to point the telescope to a different source before the current source gets covered by clouds. The all sky cameras used so far are located on La Palma at the observatory Roque de los Muchachos close to the telescopes FACT and MAGIC and the planned northern CTA site.
The lepton propagator PROPOSAL is a Monte-Carlo Simulation library written in C++, propagating high energy muons and other charged particles over large distances in media. In this article, a ...restructuring of the code is described, which yields a performance improvement of up to 30%. For an improved accuracy of the propagation processes, more exact calculations of the leptonic and hadronic decay process and more precise parametrizations for the interaction cross sections are now available. The new modular structure allows a more flexible and customized usage, which is further facilitated with a Python interface.
Program Title: PROPOSAL
Program Files doi:http://dx.doi.org/10.17632/g478pjdcxy.1
Licensing provisions: LGPL
Programming language: C++
Nature of problem: Propagation of charged particles over large distances in three dimensions through different kinds of media. These particles lose their energy stochastically via the processes of ionization, pair production, bremsstrahlung and inelastic nuclear interaction and eventually decay, producing secondary particles along the trajectory.
Solution method: Monte-Carlo simulation. The program samples the next stochastic interaction point, the type of interaction and the amount of energy lost in the interaction until either the particle decays, its energy is below a certain threshold or it reaches a given distance. To improve the performance and to deal with the bremsstrahlung divergence at small energy losses, an adaptable energy cut is used below which all losses are treated continuously. The use of interpolation tables further reduces computation time.
The sampled energy till the next stochastic loss is smeared out with a Gaussian randomization inside the physically allowed limits of the continuous losses using the second moment of the summed processes to avoid artifacts introduced by the energy cut. The deviation from a straight trajectory is evaluated using the multiple scattering calculation by Molière or the Highland parametrization, a Gaussian approximation to Molière’s theory. Multiple kinds of parametrizations are also available for bremsstrahlung, pair production and inelastic nuclear interaction to study the effects of the uncertainty of the cross sections on the propagation and further simulation steps.
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