arXiv subjects

Ralf Ulrich

Publications and source records attributed to Ralf Ulrich.

At least 19 recordsLinked to original sources

arXiv2026

Modified hadronic interactions in 3-dimensional simulations

We present a method to test the impact of ad-hoc modifications of some of the generic parameters of hadronic interactions -- cross section, elasticity, and multiplicity -- on any observable quantity using full 3-dimensional simulations of extensive air showers induced by ultra-high-energy cosmic rays. Our approach not only extends the existing 1-dimensional tools to three dimensions, but also introduces more flexible features to better respond to the needs of both theory and experiment. We first thoroughly validate the \conexD framework for the simulation of both longitudinal and lateral features of air showers, in particular for a non-standard configuration of the framework in which different energy thresholds for modifications are applied. Moreover, we show that the implementations of the ad-hoc modifications in this configuration are consistent with the previous one-dimensional simulations. Lastly, we discuss the importance of studying the interaction modifications in three dimensions and the effects of parallel modifications of multiple parameters.

astro-ph.HE↗

arXiv2025

Modified Hadronic Interactions and the future of UHECR observations

Data from multiple experiments suggest that the current interaction models used in Monte Carlo simulations do not correctly reproduce the hadronic interactions in air showers produced by ultra-high-energy cosmic rays (UHECR). We have created a large library of UHECR simulations where the interactions at the highest energies are slightly modified in various ways - but always within the constraints of the accelerator data, without any abrupt changes with energy and without assuming any specific mechanism or dramatically new physics at the ultra-high energies. Recent results of the Pierre Auger Observatory indicate a need for a change in the prediction of the models for both the muon content at ground and the depth of the maximum of longitudinal development of the shower. In our parameter space, we find combinations of modifications that are in agreement with this analysis, however a consistent description of UHECR showers remains elusive. Our library however provides a realistic representation of the freedom in the modeling of the hadronic interactions and offers an opportunity to quantify uncertainties of various predictions. This can be particularly valuable for the design of future observatories where hadronic models are often used as input for the prediction of the performance. We demonstrate this powerful capability on several selected examples.

astro-ph.HE↗

arXiv2022

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↗

arXiv2021

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↗

arXiv2021

Air shower genealogy for muon production

Measurements of the muon content of extensive air showers at the highest energies show discrepancies compared to simulations as large as the differences between proton and iron. This so-called muon puzzle is commonly attributed to a lack of understanding of the hadronic interactions in the shower development. Furthermore, measurements of the fluctuations of muon numbers suggest that the discrepancy is likely a cumulative effect of interactions of all energies in the cascade. A feature of the air shower simulation code CORSIKA 8 allows us to access all previous generations of final-state muons up to the first interaction. With this technique, we study the influence of interactions happening at any intermediate stage in the cascade on muons depending on their lateral distance in a quantitative way and compare our results with predictions of the Heitler-Matthews model.

astro-ph.HE↗

arXiv2020

Avenues to new-physics searches in cosmic ray air showers

Cosmic Rays (CR) impinging on the terrestrial atmosphere provide a viable opportunity to study new physics in hadron-nucleus collisions at energies covering many orders of magnitude, including a regime well beyond LHC energies. The permanent flux of primary CR can be used to estimate event rates for a given type of new physics scenario. As a step to estimate the potential for new-physics searches in CR-induced Extensive Air Showers (EAS), we here determine the total luminosity, including the contribution stemming from the cascade of secondaries in hadron-air interactions using Monte Carlo simulations of the hadronic shower component with CORSIKA~8. We show results obtained for single showers and discuss the interplay with the CR spectrum. Furthermore, we discuss the possibility to study BSM phenomenology in EAS, focusing on so-called large-multiplicity Higgs production as an explicit example and its impact on EAS observables.

hep-ph↗

arXiv2020

New opportunities at the photon energy frontier

Ultra-peripheral collisions (UPCs) involving heavy ions and protons are the energy frontier for photon-mediated interactions. UPC photons can be used for many purposes, including probing low-$x$ gluons via photoproduction of dijets and vector mesons, probes of beyond-standard-model processes, such as those enabled by light-by-light scattering, and studies of two-photon production of the Higgs.

hep-ph↗

arXiv2020

Self-consistent approach for measuring the energy spectra and composition of cosmic rays and determining the properties of hadronic interactions at high energy

Air showers, produced by the interaction of energetic cosmic rays with the atmosphere, are an excellent alternative to study particle physics at energies beyond any human-made particle accelerator. For that, it is necessary to identify first the mass composition of the primary cosmic ray (and its energy). None of the existing high energy interaction models have been able to reproduce coherently all air shower observables over the entire energy and zenith angle phase space. This is despite having tried all possible combinations for the cosmic ray mass composition. This proposal outlines a self-consistent strategy to study high energy particle interactions and identify the energy spectra and mass composition of cosmic rays. This strategy involves the participation of different particle accelerators and astrophysics experiments. This is important to cover the entire cosmic ray energy range and a larger phase-space of shower observables to probe the high energy interaction models.

astro-ph.HE↗

arXiv2019

Performance and science reach of POEMMA for ultrahigh-energy particles

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a potential NASA Astrophysics Probe-class mission designed to observe ultra-high energy cosmic rays (UHECRs) and cosmic neutrinos from space. POEMMA will monitor colossal volumes of the Earth's atmosphere to detect extensive air showers (EASs) produced by extremely energetic cosmic messengers: UHECRs above 20 EeV over the full sky and cosmic neutrinos above 20 PeV. We focus most of this study on the impact of POEMMA for UHECR science by simulating the detector response and mission performance for EAS from UHECRs. We show that POEMMA will provide a significant increase in the statistics of observed UHECRs at the highest energies over the entire sky. POEMMA will be the first UHECR fluorescence detector deployed in space that will provide high-quality stereoscopic observations of the longitudinal development of air showers. Therefore, it will be able to provide event-by-event estimates of the calorimetric energy and nuclear mass of UHECRs. The particle physics in the interactions limits the interpretation of the shower maximum on an event by event basis. In contrast, the calorimetric energy measurement is significantly less sensitive to the different possible final states in the early interactions. We study the prospects to discover the origin and nature of UHECRs using expectations for measurements of the energy spectrum, the distribution of arrival direction, and the atmospheric column depth at which the EAS longitudinal development reaches maximum. We also explore supplementary science capabilities of POEMMA through its sensitivity to particle interactions at extreme energies and its ability to detect ultra-high energy neutrinos and photons produced by top-down models including cosmic strings and super-heavy dark matter particle decay in the halo of the Milky Way.

astro-ph.HE↗

arXiv2019

Review of recent forward physics results from the CMS experiment

There is a rich program of forward physics measurements within the CMS Collaboration covering a wide range of topics. In many cases there is a connection to quantities and effects relevant for very high energy cosmic ray interaction. Some of the recent measurements in the fields of exclusive final states, low-pT inclusive and diffractive cross sections, underlying event, multi parton interactions, double parton scattering, final state particle correlations and minimum bias results are briefly summarized here.

hep-ex↗

arXiv2019

Core-corona effect in hadron collisions and muon production in air showers

It is very well known that the fraction of energy in a hadron collision going into electromagnetic particles (electrons and photons, including those from decays) has a large impact on the number of muons produced in air shower cascades. Recent measurements at the LHC confirm features that can be linked to a mixture of different underlying particle production mechanisms such as a collective statistical hadronization (core) in addition to the expected string fragmentation (corona). Since the two mechanisms have a different electromagnetic energy fraction, we present a possible connection between statistical hadronization in hadron collisions and muon production in air showers. Using a novel approach, we demonstrate that the core-corona effect as observed at the LHC could be part of the solution for the lack of muon production in simulations of high energy cosmic rays. To probe this hypothesis, we study hadronization in high energy hadron collisions using calorimetric information over a large range of pseudorapidity in combination with the multiplicity of central tracks. As an experimental observable, we propose the production of energy in electromagnetic particles versus hadrons, as a function of pseudorapidity and central charged particle multiplicity.

hep-ph↗

arXiv2019

CORSIKA 8 - Towards a modern framework for the simulation of extensive air showers

Current and future challenges in astroparticle physics require novel simulation tools to achieve higher precision and more flexibility. For three decades the FORTRAN version of CORSIKA served the community in an excellent way. However, the effort to maintain and further develop this complex package is getting increasingly difficult. To overcome existing limitations, and designed as a very open platform for all particle cascade simulations in astroparticle physics, we are developing CORSIKA 8 based on modern C++ and Python concepts. Here, we give a brief status report of the project.

astro-ph.IM↗

arXiv2018

Towards a Next Generation of CORSIKA: A Framework for the Simulation of Particle Cascades in Astroparticle Physics

A large scientific community depends on the precise modelling of complex processes in particle cascades in various types of matter. These models are used most prevalently in cosmic-ray physics, astrophysical-neutrino physics, and gamma-ray astronomy. In this white paper, we summarize the necessary steps to ensure the evolution and future availability of optimal simulation tools. The purpose of this document is not to act as a strict blueprint for next-generation software, but to provide guidance for the vital aspects of its design. The topics considered here are driven by physics and scientific applications. Furthermore, the main consequences of implementation decisions on performance are outlined. We highlight the computational performance as an important aspect guiding the design since future scientific applications will heavily depend on an efficient use of computational resources.

astro-ph.IM↗

arXiv2015

The FUNK search for Hidden Photon Dark Matter in the eV range

We give a brief update on the search for Hidden Photon Dark Matter with FUNK. The experiment uses a large spherical mirror, which, if Hidden Photon Dark Matter exists in the accessible mass and coupling parameter range, would yield an optical signal in the mirror's center in an otherwise dark environment. After a test run with a CCD, preparations for a run with a low-noise PMT are under way and described in this proceedings.

physics.ins-det↗

arXiv2015

Search for dark matter in the hidden-photon sector with a large spherical mirror

If dark matter consists of hidden-sector photons which kinetically mix with regular photons, a tiny oscillating electric-field component is present wherever we have dark matter. In the surface of conducting materials this induces a small probability to emit single photons almost perpendicular to the surface, with the corresponding photon frequency matching the mass of the hidden photons. We report on a construction of an experimental setup with a large ~14 m2 spherical metallic mirror that will allow for searches of hidden-photon dark matter in the eV and sub-eV range by application of different electromagnetic radiation detectors. We discuss sensitivity and accessible regions in the dark matter parameter space.

astro-ph.IM↗

arXiv2011

Anomalous Longitudinal Shower Profiles and Hadronic Interactions

The bulk of air showers initiated by very high energy cosmic rays exhibits a longitudinal development in depth with a single well-defined shower maximum. However, a small fraction of showers has a profile that differs considerably from this average behaviour. In extreme cases, such anomalous longitudinal profiles can even have two distinct shower maxima. We discuss the properties of the primary interactions that lead to such profiles. Simulations are used to estimate the rate of anomalous profiles in dependence of primary energy, mass, and characteristic features of hadronic multiparticle production at very high energies.

astro-ph.HE↗

arXiv2010

Hadronic Multiparticle Production at Ultra-High Energies and Extensive Air Showers

Studies of the nature of cosmic ray particles at the highest energies are based on the measurement of extensive air showers. Most cosmic ray properties can therefore only be obtained from the interpretation of air shower data and are thus depending on predictions of hadronic interaction models at ultra-high energies. We discuss different scenarios of model extrapolations from accelerator data to air shower energies and investigate their impact on the corresponding air shower predictions. To explore the effect of different extrapolations by hadronic interaction models we developed an ad hoc model. This ad hoc model is based on the modification of the output of standard hadronic interaction event generators within the air shower simulation process and allows us to study the impact of changing interaction features on the air shower development. In a systematic study we demonstrate the resulting changes of important air shower observables and also discuss them in terms of the predictions of the Heitler model of air shower cascades. It is found that the results of our ad hoc modifications are, to a large extend, independent of the choice of the underlying hadronic interaction model.

hep-ph↗

arXiv2009

Investigation of Hadronic Interactions at Ultra-High Energies with the Pierre Auger Observatory

The aim of the Pierre Auger Observatory is the investigation of the nature of cosmic ray particles at ultra-high energies. It can simultaneously observe the longitudinal air shower development in the atmosphere as well as particle densities on the ground. While there are no dedicated muon detectors, techniques have been developed to estimate the number of muons, $N_μ$, produced by air showers. Both, the longitudinal development, in particular the depth of the shower maximum, $X_{\rm max}$, and the muon content of air showers are highly sensitive to hadronic interactions at ultra-high energies. Currently, none of the available hadronic interaction models used for simulations of extensive air showers is able to consistently describe the observations of $X_{\rm max}$ and $N_μ$ made by the Pierre Auger Observatory.

astro-ph.HE↗