arXiv subjects

Karl-Heinz Kampert

Publications and source records attributed to Karl-Heinz Kampert.

At least 19 recordsLinked to original sources

arXiv2026

Temporal Invariance Is an Illusion: Time-Dependent Influences of the Galactic Magnetic Field on UHECR Observations

Understanding the origin of the Ultra-High-Energy Cosmic Rays (UHECRs) requires explaining the features of their energy spectrum, mass composition, and arrival directions. Current modeling approaches neglect the time evolution of UHECR observables, a factor that is particularly important in the case of bursting UHECR sources. This study focuses on the influence of time delays caused by the galactic magnetic field (GMF) on the spectrum and arrival directions of UHECRs observed on Earth. Using CRPropa 3.2, we investigate the rigidity-dependence of the residence time of extragalactic cosmic rays entering our Galaxy. We find that UHECRs entering the Milky Way can experience delays of hundreds of kiloyears relative to light, and we demonstrate that these delays significantly alter the UHECR observables. Notably, a cutoff emerges in the transient scenario within the rigidity range of $10^{18}-10^{19}$ V, which coincides with the spectral break observed in data. We find a progressive shift in composition favoring heavier nuclei, as well as a delay distribution that is correlated with GMF strength. This causes the particles to be less correlated with their initial direction the larger their delays. A dipole-like anisotropy develops over timescales of about $\sim$100 kyr in certain bursts scenarios. Our results provide an alternative explanation for the UHECR spectral cutoff that does not invoke limits on source acceleration. This could potentially revise existing constraints.

astro-ph.HE↗

arXiv2026

Modeling Gamma-Ray Bursts Using CRISP

Astrophysical neutrinos are a clear identifier of photohadronic interactions in sources of Ultra-High-Energy Cosmic Rays (UHECRs). As the Pierre Auger Observatory has shown that UHECRs exhibit a composition heavier than protons at Earth, we expect that these heavy primaries undergo nuclear cascades due to photodisintegration in the dense source environments from which they originate. In this contribution, we will derive the neutrino spectra including those originating from nuclei undergoing photohadronic interactions. This will be explored in the context of modeling the emission region of a gamma-ray burst. Photohadronic interactions will be modeled using the new framework for Cosmic Ray Stochastic Interactions for Propagation (CRISP), which employs an analytic approach to compute the underlying probabilistic description of UHECR interactions.

astro-ph.HE↗

arXiv2026

Impact of uncertainties on the cosmic optical and infrared backgrounds on the propagation of astroparticles

When propagating through the universe, gamma rays at very-high energy (VHE, E > 100 GeV) and ultra-high energy cosmic rays (UHECRs, E > 1 EeV) can interact with the optical, infrared and microwave photon fields that permeate the universe. These interactions result in a characteristic absorption imprint in the spectra of extragalactic gamma-ray sources at VHE, and in a change in the mass-composition of UHECRs. The study of both VHE gamma rays and UHECRs therefore requires precise knowledge of the intensity of the cosmic photon fields. In this work, we explore the impact of the current uncertainties on the optical and infrared photon fields on the propagation of astroparticles. We restrict the range of available models to those best matching the recent measurements, and compare the different reconstructions resulting from these models. We find that the knowledge on the cosmic background light is no longer the dominant source of uncertainties in understanding the phenomenology of astroparticle sources in the low redshift universe (z < 0.1), enabling robust spectral and composition inference with the next generation of both gamma-ray and UHECR measurements.

astro-ph.HE↗

arXiv2026

Downward ultra-high-energy neutrino detection in the air with radio antennas at ground-based observatories

Ultra-high-energy (UHE) neutrinos are unique cosmic messengers that can traverse cosmological distances unattenuated, providing direct insight into the most energetic processes in the universe. Radio detection offers significant advantages for detecting highly inclined air showers induced by UHE neutrinos. This is due to a larger exposure range compared to particle detectors, which is a result of minimal atmospheric attenuation of radio signals combined with good reconstruction precision. Furthermore, this technique improves the air shower longitudinal reconstruction, which can be used to identify neutrinos with their first interaction far below the top of the atmosphere. In this work, we present a method for identifying UHE neutrinos using ground-based radio antennas. A reconstruction algorithm is introduced based on the radio emission maximum ($X^{\text{radio}}_{\text{max}}$), which demonstrates its power in distinguishing deeply developing neutrino-induced showers from background cosmic rays. Using simulations of $ν_e$-CC-induced air showers, we evaluate the trigger efficiency, reconstruction performance, and resulting effective area and aperture prediction for a reference array. Our results show that radio detection significantly enhances the sensitivity to very inclined showers above 1 EeV, complementing traditional surface detectors. This technique is highly scalable and applicable to future radio observatories, such as GRAND. The proposed reconstruction and identification strategy provides a pathway toward achieving the sensitivity required to detect UHE neutrinos.

astro-ph.HE↗

arXiv2026

Stochastic analysis of ultra-high energy cosmic ray interactions

Photonuclear interactions between ultra-high-energy cosmic ray (UHECR) nuclei and surrounding photon fields are key to understanding the connection between the compositions observed at Earth and those emitted from the sources. These interactions can completely disintegrate a nucleus of iron over trajectory lengths of a few and up to hundreds of megaparsecs, depending on the energy of the UHECR. The stochastic nature of these interactions means that it is not possible to describe them deterministically for a single cosmic ray, and an exact formulation of the probability distributions is not yet available. Current approaches describe these interactions using either Monte Carlo simulations or solving ordinary differential equations that neglect stochasticity. Because of the limitations of these approaches, only partial capture of the process is achieved. This paper presents an analytic probabilistic description of UHECR interactions and the resulting nuclear cascades, establishing their connection to Markov jump processes. The fundamental properties of these cascades are presented, as is the computation of the usual quantities of interest, such as the horizon, spectrum, and composition. The benefits of this description are outlined using astrophysical examples related to extragalactic propagation and UHECR sources.

astro-ph.HE↗

arXiv2025

CRPropa 3.3: Toward a Unified Multi-Messenger Framework from GeV to ZeV Energies

We present CRPropa 3.3, the latest release of the publicly available Monte Carlo framework for simulating the propagation of high-energy particles in astrophysical environments. This version introduces significant extensions that enables multi-messenger studies across a broad energy range, from GeV to ZeV. New features include explicit time tracking, time-dependent advection fields, and support for position-dependent radiation backgrounds, for more realistic simulations of Galactic and extragalactic propagation. Nuclear cross sections have been updated and expanded up to lead (Z=82). We illustrate some of these new features, including acceleration at moving shocks and gamma-ray propagation in the interstellar radiation field. Together, these improvements establish CRPropa 3.3 as a comprehensive tool for modelling cosmic rays, gamma rays, and their secondaries in structured, time-dependent environments, setting the stage for next-generation multi-messenger astrophysics.

astro-ph.HE↗

arXiv2025

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↗

arXiv2025

Neutron irradiation damage on Silicon Photomultipliers and electrical annealing studies for the CBM RICH detector

Limited radiation hardness is the primary drawback to implementing Silicon Photomultipliers (SiPMs) in high-luminosity environments, such as the Compressed Baryonic Matter (CBM) experiment. Hadron irradiation generates defects in the silicon lattice of SiPMs, increasing dark current, dark count rate (DCR), crosstalk, and afterpulsing, while degrading gain and photon resolution. The expected radiation dose in the photon camera of the Ring Imaging Cherenkov detector of the CBM experiment ranges from $8\times 10^9$ to $5\times 10^{10}$ n$_{\text{eq}}$/cm$^2$ after two-months of operation at maximum beam energy and intensity. In this work, we evaluated the radiation hardness of three different SiPMs: AFBR-S4N66P024M, S14160-6050HS, and MICROFC-60035. The samples were exposed to neutron irradiation with doses ranging from $3\times 10^8$ to $1\times 10^{11}$ n$_{\text{eq}}$/cm$^2$. The neutron radiation damage was found to increase the SiPM dark current up to $10^3$ times, DCR up to $10^2$ times, and afterpulsing up to $10\%$ while decreasing their gain and photon resolution. We performed electrical annealing (250 $^{\circ}$C/30 min) on the samples to recover the photon resolution and decrease the DCR and dark current.

physics.ins-det↗

arXiv2025

Ultra-high-energy neutrino detection with radio antennas in the ground-based observatory

Ultra-high-energy (UHE) neutrinos are unique cosmic messengers that can traverse cosmological distances unattenuated, offering direct insight into the most energetic processes in the universe. Radio detection promises significant advantages for detecting highly inclined air showers induced by UHE neutrinos, including a larger exposure range compared to particle detectors, which is due to minimal atmospheric attenuation of radio signals combined with good reconstruction precision. Furthermore, this technique improves the air shower longitudinal reconstruction, which can be used to identify neutrinos with their first interaction far below the top of the atmosphere. In this work, we present a method for identifying UHE neutrinos using radio antennas deployed in ground-based observatories. We introduce a reconstruction algorithm based on the radio emission maximum ($X^{\text{radio}}_{\text{max}}$) and demonstrate its power in distinguishing deeply developing neutrino-induced showers from background cosmic rays. Using the Pierre Auger Observatory as a case study, we use the simulations of $ν_e$-CC-induced air showers and evaluate the trigger efficiency, reconstruction performance, and resulting effective area. Our results show that radio detection significantly enhances the sensitivity to very inclined showers above 1~EeV, complementing traditional surface detectors. This technique is highly scalable and applicable to future radio observatories such as GRAND. The proposed reconstruction and identification strategy provides a pathway toward achieving the sensitivity needed to detect UHE neutrinos.

astro-ph.HE↗

arXiv2025

Improving Air Shower Simulations by Tuning Pythia 8/Angantyr with Accelerator Data

We present a combined analysis of the Pythia 8 event generator using accelerator data and evaluate its impact on air shower observables. Reliable simulations with event generators are essential for particle physics analyses, achievable through advanced tuning to experimental data. Pythia 8 has emerged as a promising high-energy interaction model for cosmic ray air shower simulations, offering well-documented parameter settings and a user-friendly interface to enable automatic tuning efforts. Using data from collider and fixed-target experiments, we first derive tunes for each domain separately, before tuning both domains simultaneously. To achieve this, we define a core set of observables and quantify their dependence on selected parameters. The tuning efforts are based on gradient descent and Bayesian methods, the latter providing a full uncertainty propagation of the parameters to the observables. Results for the impact of a combined analysis for the Pythia 8/Angantyr event generator on air shower observables, such as particle densities at ground level and energy deposit profiles, are presented.

astro-ph.HE↗

arXiv2025

Uncertainties in astrophysical gamma-ray and neutrino fluxes from proton-proton cross-sections in the GeV to PeV range

The identification of Cosmic Ray (CR) sources represents one of the biggest and long-standing questions in astrophysics. Direct measurements of cosmic rays cannot provide directional information due to their deflection in (extra)galactic magnetic fields. Cosmic-ray interactions at the sources lead to the production of high-energy gamma rays and neutrinos, which, combined in the multimessenger picture, are the key to identifying the origins of CRs and estimating transport properties. While gamma-ray observations alone raise the question of whether their origin is hadronic or leptonic, the observation of high-energy neutrino emission directly points to the presence of CR hadrons. To identify the emission signatures from acceleration and transport effects a proper modeling of those interactions in a transport framework is needed. Significant work has been done to tune the production cross sections to accelerator data and different models exist that put the exact evolution of the Monte-Carlo generated showers into a statistical approach of a probabilistic description of the production of the final states of the showers relevant for astrophysical observations. In this work, we present the implementation of different hadronic interaction (HI) models into the publicly available transport code CRPropa. We apply different descriptions of the HI, trained on observational data in different energy regimes to a nearby, giant molecular cloud and the Galactic diffuse emission. In this case, the resulting gamma-ray and neutrinos fluxes can differ by a factor $\sim 2$ dependent on the choice of the HI model.

astro-ph.HE↗

arXiv2025

Photon-likeness of hadron showers and impact of Lorentz boosting

We examine the probability of proton-induced air showers at $E>10\,$EeV being misidentified as photon-induced due to neutral pions receiving a major part of the primary energy in the first interaction, thereby enhancing the electromagnetic shower component by their $π^0 \to γγ$ decay. Using CORSIKA simulations, we demonstrate the relevance of this effect at EeV energies. However, the probability for such photon-like events drops down strongly at the highest energies due to the increasing probability of Lorentz boosted $π^0$'s suffering hadronic interactions before decay. Different hadronic interaction models suggest that photon-like hadronic events may be observed at current UHECR observatories. A quantitative comparison of the observed number of background events found in recent photon searches published by the Pierre Auger Collaboration allows us conclude that the hypothesis of upwards fluctuations of $π^0$-production alone is insufficient to explain the data.

hep-ph↗

arXiv2025

Flow and Equation of State of nuclear matter at $\mathbf{E_{\mathrm{kin}}}$/A=0.25-1.5 GeV with the SMASH transport approach

We present a comparison of directed and elliptic flow data by the FOPI collaboration in Au--Au, Xe--CsI, and Ni--Ni collisions at beam kinetic energies from 0.25 to 1.5 GeV per nucleon to simulations using the SMASH hadronic transport model. The Equation of State is parameterized as a function of nuclear density and momentum dependent potentials are newly introduced in SMASH. With a statistical analysis, we show that within the present status of the SMASH transport model, the collective flow data at lower energies is in the best agreement with a soft momentum dependent potential, while the elliptic flow at higher energies requires a harder momentum dependent Equation of State.

nucl-th↗

arXiv2025

Ideas and Requirements for the Global Cosmic-Ray Observatory (GCOS)

After a successful kick-off meeting in 2021. two workshops in 2022 and 2023 on the future Global Cosmic-Ray Observatory (GCOS) focused mainly on a straw man design of the detector and science possibilities for astro- and particle physics. About 100 participants gathered for in-person and hybrid panel discussions. In this report, we summarize these discussions, present a preliminary straw-man design for GCOS and collect short write-ups of the flash talks given during the focus sessions.

astro-ph.IM↗

arXiv2024

Modified temperature redshift relation and UHECR propagation

We re-examine the interactions of ultra-high energy cosmic rays (UHECRs) with photons from the cosmic microwave background (CMB) under a changed, locally non-linear temperature redshift relation $T(z)$. This changed temperature redshift relation has recently been suggested by the postulate of subjecting thermalised and isotropic photon gases such as the CMB to an SU(2) rather than a U(1) gauge group. This modification of $Λ$CDM is called SU(2)$_{\rm CMB}$, and some cosmological parameters obtained by SU(2)$_{\rm CMB}$ seem to be in better agreement with local measurements of the same quantities, in particular $H_0$ and S$_8$. In this work, we apply the reduced CMB photon density under SU(2)$_{\rm CMB}$ to the propagation of UHECRs. This leads to a higher UHECR flux just below the ankle in the cosmic ray spectrum and slightly more cosmogenic neutrinos under otherwise equal conditions for emission and propagation. Most prominently, the proton flux is significantly increased below the ankle ($5\times10^{18}$ eV) for hard injection spectra and without considering the effects of magnetic fields. The reduction in CMB photon density also favours a decreased cosmic ray source evolution than the best fit using $Λ$CDM. In consequence, it seems that SU(2)$_{\rm CMB}$ favours sources that evolve as the star formation rate (SFR), like starburst galaxies (SBG) and gamma-ray bursts (GRB), over active galactic nuclei (AGNs) as origins of UHECRs. We conclude that the question about the nature of primary sources of UHECRs is directly affected by the assumed temperature redshift relation of the CMB.

astro-ph.HE↗

arXiv2023

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↗

arXiv2023

CRPropa 3.2: a public framework for high-energy astroparticle simulations

CRPropa is a Monte Carlo framework for simulating the propagation of (ultra-) high-energy particles in the Universe, including cosmic rays, gamma rays, electrons, and neutrinos. It covers energies from ZeV down to GeV for gamma rays and electrons, and TeV for cosmic rays and neutrinos, supporting various astrophysical environments such as the surroundings of astrophysical sources, galactic, and extragalactic environments. The newest version, CRPropa 3.2, represents a significant leap forward towards a universal multi-messenger framework, opening up the possibility for many more astrophysical applications. This includes extensions to simulate cosmic-ray acceleration and particle interactions within astrophysical source environments, a full Monte Carlo treatment of electromagnetic cascades, improved ensemble-averaged Galactic propagation, significant performance improvements for cosmic-ray tracking through magnetic fields, and a user-friendly implementation of custom photon fields, among many more enhancements. This contribution will give an overview of the new features and present several applications to cosmic-ray and gamma-ray propagation.

astro-ph.HE↗

arXiv2022

Report of the Topical Group on Cosmic Probes of Fundamental Physics for for Snowmass 2021

Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves. Already today, these probes give access to fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model. The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves. The scope for major developments in the next decades is dramatic, as we detail in this report.

hep-ph↗