Computational Methods in Science and Engineering : Proceedings of the Workshop SimLabs@KIT, November 29 - 30, 2010, Karlsruhe, Germany

In this proceedings volume we provide a compilation of article contributions equally covering applications from different research fields and ranging from capacity up to capability computing. Besides classical computing aspects such as parallelization, the focus of these proceedings is on multi-scale approaches and methods for tackling algorithm and data complexity. Also practical aspects regarding the usage of the HPC infrastructure and available tools and software at the SCC are presented

Density of GeV muons in air showers measured with IceTop

We present a measurement of the density of GeV muons in near-vertical air showers using three years of data recorded by the IceTop array at the South Pole. Depending on the shower size, the muon densities have been measured at lateral distances between 200 and 1000 m. From these lateral distributions, we derive the muon densities as functions of energy at reference distances of 600 and 800 m for primary energies between 2.5 and 40 PeV and between 9 and 120 PeV, respectively. The muon densities are determined using, as a baseline, the hadronic interaction model Sibyll 2.1 together with various composition models. The measurements are consistent with the predicted muon densities within these baseline interaction and composition models. The measured muon densities have also been compared to simulations using the post-LHC models EPOS-LHC and QGSJet-II.04. The result of this comparison is that the post-LHC models together with any given composition model yield higher muon densities than observed. This is in contrast to the observations above 1 EeV where all model simulations yield for any mass composition lower muon densities than the measured ones. The post-LHC models in general feature higher muon densities so that the agreement with experimental data at the highest energies is improved but the muon densities are not correct in the energy range between 2.5 and about 100 PeV

Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider

Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton–proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments—as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER—to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity 'dark showers', highlighting opportunities for expanding the LHC reach for these signals

Detector Simulation Challenges for Future Accelerator Experiments

Detector simulation is a key component for studies on prospective future high-energy colliders, the design, optimization, testing and operation of particle physics experiments, and the analysis of the data collected to perform physics measurements. This review starts from the current state of the art technology applied to detector simulation in high-energy physics and elaborates on the evolution of software tools developed to address the challenges posed by future accelerator programs beyond the HL-LHC era, into the 2030–2050 period. New accelerator, detector, and computing technologies set the stage for an exercise in how detector simulation will serve the needs of the high-energy physics programs of the mid 21st century, and its potential impact on other research domains

The air shower simulation framework CORSIKA 8: Development and first applications to muon production

Tools to accurately simulate extensive air showers are a key asset for the understanding of ultra-high energy cosmic rays. In this thesis, the Monte Carlo air shower simulation framework CORSIKA 8 is presented. CORSIKA 8 constitutes a next-generation code that aims to combine new functionality with a high level of flexibility and modularity. Notable aspects include the ability to freely combine an arbitrary number of physical processes and to setup simulation environments consisting of several media, including custom atmospheric models. A special feature is the possibility to inspect the complete lineage of particles, which allows linking particles on ground with any of their preceding generations. After describing the foundations of Monte Carlo shower simulations, I explain the architecture of CORSIKA 8 in depth. Focusing on the hadronic and muonic shower components, results obtained with CORSIKA 8 and other simulation codes are compared with each other. Even when using the same hadronic interaction models, a number of differences are observed, in particular regarding low-energy interactions, which have a considerable impact on the lateral distribution of muons at kilometre-scale distances up to a factor of two and more. Making use of the lineage technique, I study the phase space of hadronic interactions in order to quantify the importance for muon production and compare the results with the Heitler–Matthews toy model. At high energies (√s ≳ 500 GeV) particle production in the forward region is confirmed to be especially important, while the central region becomes relevant at low energies (√s ≲ 50 GeV) in particular for muons at large distances. Additionally, I study the impact of modified hadronic interactions on air shower observables. Modified hadron-air cross-sections mainly affect the longitudinal development, causing a larger shift of the maximum muon production depth than of the shower maximum. Artificially increased ρ 0 production, on the other hand, can greatly increase the number of muons with only small impact on other observables. Finally, I also consider the possibility of large multiplicity boson production in the first interaction and study its phenomenology in air showers with a simple toy model. Within the scope of this thesis, I developed the foundations of the CORSIKA 8 framework. Based on the studies that have become possible with CORSIKA 8, I point out some new opportunities towards an improved understanding of muons in air showers

Sensitivity and background estimates towards Phase-I of the COMET muon-to-electron conversion search

COMET is a future high-precision experiment searching for charged lepton flavour violation through the muon-to-electron conversion process. It aims to push the intensity frontier of particle physics by coupling an intense muon beam with cutting-edge detector technology. The first stage of the experiment, COMET Phase-I, is currently being assembled and will soon enter its data acquisition period. It plans to achieve a single event sensitivity to μ-e conversion in aluminium of 3.1x10⁻¹⁵. This thesis presents a study of the sensitivity and backgrounds of COMET Phase-I using the latest Monte Carlo simulation data produced. The background contribution from cosmic ray-induced atmospheric muons is estimated using a backward Monte Carlo approach, which allows computational resources to be focused on the most critical signal-mimicking events. Analysis of a μ-e conversion simulation sample suggests that COMET Phase-I will reach a single event sensitivity of 3.6x10⁻¹⁵ within 146 days of data acquisition. Our results suggest that, in that period, on the order of 10³ atmospheric muons will enter the detector system and produce an event similar enough to the conversion signal to pass all the signal selection criteria. Most of these events will be rejected by the Cosmic Ray Veto system, however, we expect at least 2.2 background events to sneak in unnoticed. It is vital for the conversion search that these events be discriminated from conversion electrons, for instance by using Cherenkov threshold counters to distinguish between muons and electrons or, alternatively, by developing a direction identification algorithm to reject some fraction of the μ⁺-induced events.Open Acces

EuCAPT White Paper: Opportunities and Challenges for Theoretical Astroparticle Physics in the Next Decade

Astroparticle physics is undergoing a profound transformation, due to a series of extraordinary new results, such as the discovery of high-energy cosmic neutrinos with IceCube, the direct detection of gravitational waves with LIGO and Virgo, and many others. This white paper is the result of a collaborative effort that involved hundreds of theoretical astroparticle physicists and cosmologists, under the coordination of the European Consortium for Astroparticle Theory (EuCAPT). Addressed to the whole astroparticle physics community, it explores upcoming theoretical opportunities and challenges for our field of research, with particular emphasis on the possible synergies among different subfields, and the prospects for solving the most fundamental open questions with multi-messenger observations.Comment: White paper of the European Consortium for Astroparticle Theory (EuCAPT). 135 authors, 400 endorsers, 133 pages, 1382 reference