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Wolfgang Rhode

Publications and source records attributed to Wolfgang Rhode.

At least 19 recordsLinked to original sources

PhysAttNet: Enhancing Predictive Performance in Industrial and Astrophysical Time Series via Physics-Informed Attention

Accurate and robust time series forecasting is essential in many applications involving physical processes, such as manufacturing monitoring and astrophysical event detection. In these settings, predictive models must remain reliable under noise, variability, and measurement uncertainty while capturing temporally localized structures corresponding to physically meaningful events. Convolutional neural networks (CNNs) are widely used for such tasks due to their computational efficiency and strong representational capacity. However, their learned temporal representations often exhibit unstable or physically inconsistent attention patterns, reducing robustness, generalization, and interpretability. This paper introduces PhysAttNet, a physics-informed attention framework for time series forecasting. PhysAttNet augments a lightweight CNN forecaster with an attention head guided by domain-informed regularization reflecting the structural properties of physical signals. Specifically, three complementary constraints are imposed during training: an alignment regularization that encourages attention to follow smooth, peak-centered temporal structures derived from the input signal, a smoothness regularization that enforces continuous temporal evolution, and a sparsity regularization that promotes selective focus on informative intervals. These differentiable regularization terms introduce physics-guided inductive bias without requiring annotated explanations or manual supervision. Experiments on two distinct applications, namely predicting cutting forces during milling and forecasting flares in blazar time series, demonstrate that PhysAttNet improves forecasting accuracy, generalization, and prediction performance on structurally important events.

cs.LG

Road map for the tuning of hadronic interaction models with accelerator-based and astroparticle data

In high-energy and astroparticle physics, event generators play an essential role, even in the simplest data analyses. As analysis techniques become more sophisticated, e.g. based on deep neural networks, their correct description of the observed event characteristics becomes even more important. Physical processes occurring in hadronic collisions are simulated within a Monte Carlo framework. A major challenge is the modeling of hadron dynamics at low momentum transfer, which includes the initial and final phases of every hadronic collision. QCD-inspired phenomenological models used for these phases cannot guarantee completeness or correctness over the full phase space. These models usually include parameters which must be tuned to suitable experimental data. Until now, event generators have been developed and tuned mainly on the basis of data from high-energy physics experiments at accelerators. The wealth of data available from the latest generation of astroparticle experiments has not yet been fully exploited, and in many cases is not satisfactorily described. Both kinds of data sets are complementary as astroparticle experiments provide sensitivity especially to hadrons produced nearly parallel to the collision axis and cover center-of-mass energies up to several hundred TeV, well beyond those reached at colliders so far. In this report, we provide an overview of state-of-the-art event generators and their tuning, including the most relevant inputs from high-energy accelerator and astroparticle experiments. We present a road map that shows, for the first time, how the unified tuning of event generators with accelerator-based and astroparticle data can be performed.

astro-ph.HE

Combining IceCube Muon Tracks and Cascades to measure the Galactic Diffuse Neutrino Flux

The diffuse Galactic neutrino flux is produced by cosmic rays interacting with the interstellar medium. The measurement of this flux can help to understand the distribution of cosmic rays in the Galaxy. The first observation of this neutrino flux was published in 2023 by the IceCube Collaboration. Here, plans for a new analysis combining different event topologies are presented. IceCube measures events in two main topologies. Tracks, originating in charged current $\nu_\mu$ interactions, provide a better angular resolution. In contrast, cascades, from most other possible interactions, provide a better energy resolution and are able to observe the Southern sky (and therefore the Galactic Center) despite the huge background of atmospheric muons. Combining both event topologies in one analysis exploits all these advantages. Sensitivities and model discrimination power of a combined measurement using a forward folding binned likelihood fit are discussed here.

astro-ph.HE

Cosmic-ray propagation features in gamma-ray measurements

Gamma-ray measurements from GeV to PeV energies have provided us with a wealth of information on diffuse emission and sources in the Universe lately. With improved spatial and temporal resolutions together with real-time multimessenger astronomy, the modeling of 3D cosmic-ray transport becomes more and more important to explain the data. Here, we will give a compact summary of how cosmic-ray propagation in very different astrophysical environments like the Sun, Milky Way, and active galaxies can be constrained by combining 3D modeling with the propagation software CRPropa with gamma-ray measurements.

astro-ph.HE

Prompt and Conventional High-Energy Muon Spectra from a full Monte Carlo Simulation via $\texttt{CORSIKA7}$

Extensive air showers produce high-energy muons that can be utilized to probe hadronic interaction models in cosmic ray interactions. Most muons originate from pion and kaon decays, called $\textit{conventional}$ muons, while a smaller fraction, referred to as $\textit{prompt}$ muons, arises from the decay of heavier, short-lived hadrons. The $\texttt{EHISTORY}$ option of the air shower simulation tool $\texttt{CORSIKA7}$ is used in this work to investigate the prompt and conventional muon flux in the energy range of 100 TeV to 100 PeV, utilizing the newly developed open-source python software $\texttt{PANAMA}$. Identifying the muon parent particles allows for scaling the contribution of prompt particles, which can be leveraged by future experimental analyses to measure the normalization of the prompt muon flux. Obtained prompt muon spectra from $\texttt{CORSIKA7}$ are compared to $\texttt{MCEq}$ results. The relevance to large-volume neutrino detectors, such as IceCube and KM3NeT, and the connection to hadronic interaction models is discussed.

astro-ph.HE

Improvements in charged lepton and photon propagation for the software PROPOSAL

Accurate particle simulations are essential for the next generation of experiments in astroparticle physics. The Monte Carlo simulation library PROPOSAL is a flexible tool to efficiently propagate high-energy leptons and photons through large volumes of media, for example in the context of underground observatories. It is written as a C++ library, including a Python interface. In this paper, the most recent updates of PROPOSAL are described, including the addition of electron, positron, and photon propagation, for which new interaction types have been implemented. This allows the usage of PROPOSAL to simulate electromagnetic particle cascades, for example in the context of air shower simulations. The precision of the propagation has been improved by including rare interaction processes, new photonuclear parametrizations, deflections in stochastic interactions, and the possibility of propagating in inhomogeneous density distributions. Additional technical improvements regarding the interpolation routine and the propagation algorithm are described.

astro-ph.IM

The Relevance of Muon Deflections for Neutrino Telescopes

Large-scale neutrino telescopes have the primary objective to detect and characterize neutrino sources in the universe. These experiments rely on the detection of charged leptons produced in the interaction of neutrinos with nuclei. Angular resolutions are estimated to be better than 1 degree, which is achieved by the reconstruction of muons. This angular resolution is a measure of the accuracy with which the direction of incoming neutrinos can be determined. Since muons can traverse distances of several kilometers through media, the original muon direction can differ from the muon direction inside the detector due to deflections by stochastic interactions and multiple scattering. In this contribution, a recently published study of muon deflections based on the simulation tool PROPOSAL is presented. Muons with various energies are propagated through different media over several distances. Data-Monte-Carlo comparisons as well as comparisons to the simulation tools MUSIC and Geant4 are performed. Finally, the impact of muon deflections on large-scale neutrino telescopes is discussed.

hep-ex

Simulation of Deflection Uncertainties on Directional Reconstructions of Muons Using PROPOSAL

Large scale neutrino detectors and muon tomography rely on the muon direction in the detector to infer the muon's or parent neutrino's origin. However, muons accumulate deflections along their propagation path prior to entering the detector, which may need to be accounted for as an additional source of uncertainty. In this paper, the deflection of muons is studied with the simulation tool PROPOSAL, which accounts for multiple scattering and deflection on stochastic interactions. Deflections along individual interactions depend on the muon energy and the interaction type, and can reach up to the order of degrees -- even at TeV to PeV energies. The accumulated deflection angle can be parametrized in dependence of the final muon energy, independent of the initial muon energy. The median accumulated deflection of a propagated muon with a final energy of 500 GeV is $θ_{\text{acc}} = 0.10°$ with a 99 % central interval of $[0.01°, 0.39°]$. This is on the order of magnitude of the directional resolution of present neutrino detectors. Furthermore, comparisons with the simulation tools MUSIC and Geant4 as well as two different muon deflection measurements are performed.

astro-ph.IM

Performance of a Small Array of Imaging Air Cherenkov Telescopes sited in Australia

As TeV gamma-ray astronomy progresses into the era of the Cherenkov Telescope Array (CTA), there is a desire for the capacity to instantaneously follow up on transient phenomena and continuously monitor gamma-ray flux at energies above $10^{12}$ eV. To this end, a worldwide network of Imaging Air Cherenkov Telescopes (IACTs) is required to provide triggers for CTA observations and complementary continuous monitoring. An IACT array sited in Australia would contribute significant coverage of the Southern Hemisphere sky. Here, we investigate the suitability of a small IACT array and how different design factors influence its performance. Monte Carlo simulations were produced based on the Small-Sized Telescope (SST) and Medium-Sized Telescope (MST) designs from CTA. Angular resolution improved with larger baseline distances up to 277m between telescopes, and energy thresholds were lower at 1000m altitude than at 0m. The $\sim$300 GeV energy threshold of MSTs proved more suitable for observing transients than the $\sim$1.2 TeV threshold of SSTs. An array of four MSTs at 1000m was estimated to give a 5.7$σ$ detection of an RS Ophiuchi-like nova eruption from a 4-hour observation. We conclude that an array of four MST-class IACTs at an Australian site would ideally complement the capabilities of CTA.

astro-ph.IM

Rapid X-ray Variability in Mkn 421 during a Multiwavelength Campaign

The study of short-term variability properties in AGN jets has the potential to shed light on their particle acceleration and emission mechanisms. We report results from a four-day coordinated multi-wavelength campaign on the highly-peaked blazar (HBL) Mkn 421 in 2019 January. We obtained X-ray data from AstroSAT, BVRI photometry with the Whole Earth Blazar Telescope (WEBT), and TeV data from FACT to explore short-term multi-wavelength variability in this HBL. The X-ray continuum is rapidly variable on time-scales of tens of ks. Fractional variability amplitude increases with energy across the synchrotron hump, consistent with previous studies; we interpret this observation in the context of a model with multiple cells whose emission spectra contain cutoffs that follow a power-law distribution. We also performed time-averaged and time-resolved (time-scales of 6 ks) spectral fits; a broken power-law model fits all spectra well; time-resolved spectral fitting reveals the usual hardening when brightening behaviour. Intra-X-ray cross correlations yield evidence for the 0.6-0.8 keV band to likely lead the other bands by an average of 4.6 +- 2.6 ks, but only during the first half of the observation. The source displayed minimal night-to-night variability at all wavebands thus precluding significant interband correlations during our campaign. The broadband SED is modeled well with a standard one-zone leptonic model, yielding jet parameters consistent with those obtained from previous SEDs of this source.

astro-ph.HE

The Muon Puzzle in cosmic-ray induced air showers and its connection to the Large Hadron Collider

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 eventually decay into muons. 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. The origin of this discrepancy has been traced to the composition of secondary particles in hadronic interactions. The muon discrepancy starts at the TeV scale, which suggests that this change in hadron composition is observable at the Large Hadron Collider. An effect that can potentially explain the puzzle has been discovered at the LHC, but needs to be confirmed for forward produced hadrons with LHCb, and with future data on oxygen beams.

astro-ph.HE

Deep Learning-based Imaging in Radio Interferometry

The sparse layouts of radio interferometers result in an incomplete sampling of the sky in Fourier space which leads to artifacts in the reconstructed images. Cleaning these systematic effects is essential for the scientific use of radiointerferometric images. Established reconstruction methods are often time-consuming, require expert-knowledge, and suffer from a lack of reproducibility. We have developed a prototype Deep Learning-based method that generates reproducible images in an expedient fashion. To this end, we take advantage of the efficiency of Convolutional Neural Networks to reconstruct image data from incomplete information in Fourier space. The Neural Network architecture is inspired by super-resolution models that utilize residual blocks. Using simulated data of radio galaxies that are composed of Gaussian components we train Deep Learning models whose reconstruction capability is quantified using various measures. The reconstruction performance is evaluated on clean and noisy input data by comparing the resulting predictions with the true source images. We find that source angles and sizes are well reproduced, while the recovered fluxes show substantial scatter, albeit not worse than existing methods without fine-tuning. Finally, we propose more advanced approaches using Deep Learning that include uncertainty estimates and a concept to analyze larger images.

astro-ph.IM

CORSIKA 8 -- Contributions to the 37th International Cosmic Ray Conference in Berlin Germany (ICRC 2021)

Compilation of the six contributions to the ICRC conference 2021 by the CORSIKA 8 Collaboration. The status of the project is illustrated. In particular, the secondary hadron as well as the electromagnetic cascades are being validated individually, and current results are reviewed. A novel framework for radio emission simulations is presented, which is designed given the modular nature of CORSIKA 8 to support, both, the CoREAS as well as the ZHS formalism. At the same time, first Cherenkov emission calculations are shown which are based on CORSIKA 8 coupled with a GPU Cherenkov emission code. Finally, a new powerful feature of CORSIKA 8 is illustrated, where the entire genealogy of air shower particles can be studied in all details.

astro-ph.HE

Long-term multi-band photometric monitoring of Mrk 501

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. 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. 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.

astro-ph.HE

Statistical properties of flux variations in blazar light curves at GeV and TeV energies

Despite numerous detections of individual flares, the physical origin of the rapid variability observed from blazars remains uncertain. Using Bayesian blocks and the Eisenstein-Hut HOP algorithm, we characterize flux variations of high significance in the $γ$-ray light curves of two samples of blazars. Daily binned long-term light curves of TeV-bright blazars observed with the First G-APD Cherenkov Telescope (FACT) are compared to those of GeV-bright blazars observed with the Large Area Telescope on board the $Fermi$ Gamma-ray Space Telescope ($Fermi$-LAT). We find no evidence for systematic asymmetry of the flux variations based on the derived rise and decay time scales. Additionally, we show that the daily-binned blazar light curves can be described by an exponential stochastic Ornstein-Uhlenbeck (OU) process with parameters depending on energy. Our analysis suggests that the flux variability in both samples is a superposition of faster fluctuations. This is, for instance, challenging to explain by shock-acceleration but expected for magnetic reconnection.

astro-ph.HE

Detection of Small Scale Components in Power Law Spectra

Spectra in astroparticle physics are commonly approximated by simple power laws. The steeply falling nature of these power laws, however, makes the detection of additional components rather challenging. This holds true especially, if the additional components are small compared to the established ones. Energy spectra of muon neutrinos are an interesting example of such a scenario, where the conventional and astrophysical components to the spectra have been established by the use of different analysis methods, such as likelihood fits or spectral deconvolution. The prompt component, although expected from theoretical models, has not yet been experimentally observed. Furthermore, the extraction of physics parameters is challenged by the large systematic uncertainties, especially at high energies. This contribution presents a different approach to the analysis of power-law spectra, which is based on functional data analysis. The method itself and its implications are discussed using muon and neutrino energy spectra as an example.

astro-ph.HE

Relentless multi-wavelength variability of Mrk 421 and Mrk 501

Mrk 421 and Mrk 501 are two close, bright and well-studied high-synchrotron-peaked blazars, which feature bright and persistent GeV and TeV emission. We use the longest and densest dataset of unbiased observations of these two sources, obtained at TeV and GeV energies during five years with FACT and Fermi-LAT. To characterize the variability and derive constraints on the emission mechanism, we augment the dataset with contemporaneous multi-wavelength observations from radio to X-rays. We correlate the light curves, identify individual flares in TeV energies and X-rays, and look for inter-band connections, which are expected from the shock propagations within the jet. For Mrk 421, we find that the X-rays and TeV energies are well correlated with close to zero lag, supporting the SSC emission scenario. The timing between the TeV, X-ray flares in Mrk 421 is consistent with periods expected in the case of Lense-Thirring precession of the accretion disc. The variability of Mrk 501 on long-term periods is also consistent with SSC, with a sub-day lag between X-rays and TeV energies. Fractional variability for both blazars shows a two bump structure with the highest variability in the X-ray and TeV bands.

astro-ph.HE

The relentless variability of Mrk 421 from the TeV to the radio

The origin of the gamma-ray emission of the blazar Mrk 421 is still a matter of debate. We used 5.5 years of unbiased observing campaign data, obtained using the FACT telescope and the Fermi LAT detector at TeV and GeV energies, the longest and densest so far, together with contemporaneous multi-wavelength observations, to characterise the variability of Mrk 421 and to constrain the underlying physical mechanisms. We studied and correlated light curves obtained by ten different instruments and found two significant results. The TeV and X-ray light curves are very well correlated with a lag of <0.6 days. The GeV and radio (15 Ghz band) light curves are widely and strongly correlated. Variations of the GeV light curve lead those in the radio. Lepto-hadronic and purely hadronic models in the frame of shock acceleration predict proton acceleration or cooling timescales that are ruled out by the short variability timescales and delays observed in Mrk 421. Instead the observations match the predictions of leptonic models.

astro-ph.HE