Leander Fischer
A5085941121- Astrophysics and Cosmic Phenomena
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Particle physics theoretical and experimental studies
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Radio Wave Propagation Studies
- Gyrotron and Vacuum Electronics Research
- Particle Detector Development and Performance
- Precipitation Measurement and Analysis
- Solar and Space Plasma Dynamics
- Radio, Podcasts, and Digital Media
- Atmospheric Ozone and Climate
- Particle accelerators and beam dynamics
- Cryospheric studies and observations
- Ionosphere and magnetosphere dynamics
- Radiation Detection and Scintillator Technologies
- History and Developments in Astronomy
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Nuclear reactor physics and engineering
- Advanced Optical Sensing Technologies
- Soil Moisture and Remote Sensing
Deutsches Elektronen-Synchrotron DESY
2021-2025
The University of Texas at Arlington
2021-2024
Lawrence Berkeley National Laboratory
2023-2024
Southern University and Agricultural and Mechanical College
2021-2024
Clark Atlanta University
2021-2024
University of Alaska Anchorage
2021-2024
Providence College
2021-2024
UCLouvain
2023
TU Dortmund University
2023
Drexel University
2023
The IceCube Neutrino Observatory has established the existence of a high-energy all-sky neutrino flux astrophysical origin. This discovery was made using events interacting within fiducial region detector surrounded by an active veto and with reconstructed energy above 60 TeV, commonly known as starting event sample, or HESE. We revisit analysis HESE sample additional 4.5 years data, newer glacial ice models, improved systematics treatment. paper describes in detail, reports on latest...
Gamma-ray bursts (GRBs) have long been considered a possible source of high-energy neutrinos. While no correlations yet detected between neutrinos and GRBs, the recent observation GRB 221009A - brightest observed by Fermi-GBM to date first one be above an energy 10 TeV provides unique opportunity test for hadronic emission. In this paper, we leverage wide range IceCube Neutrino Observatory search from 221009A. We find significant deviation background expectation across event samples ranging...
Continued improvements on existing reconstruction methods are vital to the success of high-energy physics experiments, such as IceCube Neutrino Observatory. In IceCube, further challenges arise detector is situated at geographic South Pole where computational resources limited. However, perform real-time analyses and issue alerts telescopes around world, powerful fast desired. Deep neural networks can be extremely powerful, their usage computationally inexpensive once trained. These...
Gamma-ray bursts (GRBs) are considered as promising sources of ultra-high-energy cosmic rays (UHECRs) due to their large power output. Observing a neutrino flux from GRBs would offer evidence that hadronic accelerators UHECRs. Previous IceCube analyses, which primarily focused on neutrinos arriving in temporal coincidence with the prompt gamma rays, found no significant excess. The four analyses presented this paper extend region interest 14 days before and after phase, including generic...
Abstract The IceCube Neutrino Observatory sends realtime neutrino alerts with a high probability of being astrophysical in origin. We present new method to correlate these events and possible candidate sources using 2089 blazars from the Fermi-LAT 4LAC-DR2 catalog 3413 active galactic nuclei (AGNs) Radio Fundamental Catalog. No statistically significant emission was found any searches. result suggests that small fraction, <1%, studied AGNs emit neutrinos pass alert criteria, is compatible...
We describe a new data sample of IceCube DeepCore and report on the latest measurement atmospheric neutrino oscillations obtained with recorded between 2011--2019. The includes significant improvements in calibration, detector simulation, processing, analysis benefits from sophisticated treatment systematic uncertainties, significantly greater level detail since our last study. By measuring relative fluxes flavors as function their reconstructed energies arrival directions we constrain...
We report on a measurement of astrophysical tau neutrinos with 9.7 yr IceCube data. Using convolutional neural networks trained images derived from simulated events, seven candidate ν_{τ} events were found visible energies ranging roughly 20 TeV to 1 PeV and median expected parent energy about 200 TeV. Considering backgrounds atmospheric neutrinos, muons π^{±}/K^{±} decays in air showers, we obtain total estimated background 0.5 dominated by non-ν_{τ} neutrinos. Thus, rule out the absence at...
Abstract We present the results of a search for 10–1000 GeV neutrinos from 2268 gamma-ray bursts (GRBs) over 8 yr IceCube-DeepCore data. This work probes burst physics below photosphere where electromagnetic radiation cannot escape. Neutrinos tens giga electronvolts are predicted in sub-photospheric collision free-streaming neutrons with bulk-jet protons. In first analysis, we searched most significant neutrino-GRB coincidence using six overlapping time windows centered on prompt phase each...
High-energy tau neutrinos are rarely produced in atmospheric cosmic-ray showers or at cosmic particle accelerators, but expected to emerge during neutrino propagation over distances due flavor mixing. When high energy interact inside the IceCube detector, two spatially separated depositions may be resolved, first from charged current interaction and second lepton decay. We report a novel analysis of 7.5 years data that identifies candidate among 60 ``High-Energy Starting Events'' (HESE)...
The flux of high-energy neutrinos passing through the Earth is attenuated due to their interactions with matter. interaction rate modulated by neutrino cross section and affects arriving at IceCube Neutrino Observatory, a cubic-kilometer detector embedded in Antarctic ice sheet. We present measurement between 60 TeV 10 PeV using starting events (HESE) sample from 7.5 years data. result binned energy obtained both Bayesian frequentist statistics. find it compatible predictions Standard Model....
Abstract Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube data and catalog containing more than 1000 core-collapse types IIn IIP sample stripped-envelope supernovae. search both emission from individual as well combined the whole supernova sample, through stacking analysis. No significant spatial or temporal neutrinos with cataloged was found. All scenarios were tested against background expectation...
Abstract In this work, we present the results of searches for signatures dark matter decay or annihilation into Standard Model particles, and secret neutrino interactions with matter. Neutrinos could be produced in galactic extragalactic Additionally, if an interaction between neutrinos exists then will interact neutrinos. particular induce anisotropy sky is present. We use seven a half years High-Energy Starting Event (HESE) sample data, which measures energy range approximately 60 TeV to...
We report constraints on nonstandard neutrino interactions (NSI) from the observation of atmospheric neutrinos with IceCube, limiting all individual coupling strengths a single dataset. Furthermore, IceCube is first experiment to constrain flavor-violating and nonuniversal couplings simultaneously. Hypothetical NSI are generically expected arise due exchange new heavy mediator particle. Neutrinos propagating in matter scatter off fermions forward direction negligible momentum transfer. Hence...
IceCube has performed several all-sky searches for point-like neutrino sources using track-like events, including a recent time-integrated analysis 10 years of data. This paper accompanies the public data release these candidates detected by between April 6, 2008 and July 8, 2018. The selection includes through-going tracks, primarily due to muon candidates, that reach detector from all directions, as well track events start within instrumented volume. An updated reconstruction taken after...
Beginning in 2016, the IceCube Neutrino Observatory has sent out alerts real time containing information of high-energy ($E \gtrsim 100$~TeV) neutrino candidate events with moderate-to-high ($\gtrsim 30$\%) probability astrophysical origin. In this work, we use a recent catalog such alert events, which, addition to announced real-time, includes that were identified retroactively, and covers period 2011-2020. We also search for additional, lower-energy, neutrinos from arrival directions these...
Abstract IceCube alert events are neutrinos with a moderate-to-high probability of having astrophysical origin. In this study, we analyze 11 yr data and investigate 122 selection high-energy tracks detected between 2009 the end 2021. This event (alert + tracks) has an average ≥0.5 being We search for additional continuous transient neutrino emission within events’ error regions. find no evidence significant from any directions. The only locally is associated blazar TXS 0506+056, local...
In multi-messenger astronomy, rapid investigation of interesting transients is imperative. As an observatory with a 4$\pi$ steradian field view and $\sim$99\% uptime, the IceCube Neutrino Observatory unique facility to follow up transients, provide valuable insight for other observatories inform their observing decisions. Since 2016, has been using low-latency data rapidly respond astrophysical events reported by observational community. Here, we describe pipeline used perform these analyses...
Abstract IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole. The main goal of detection astrophysical neutrinos and identification their sources. High-energy muon are observed via secondary muons produced in charge current interactions with nuclei ice. Currently, best performing track directional reconstruction based on maximum likelihood method using arrival time distribution photons registered by experiment's photomultipliers. A known systematic shortcoming...
Abstract. The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected propagation effect observed experiment is an anisotropic attenuation, which aligned with local flow direction ice. We examine birefringent through polycrystalline microstructure as a possible explanation for this effect. predictions first-principles model developed...
Abstract Galactic PeV cosmic-ray accelerators (PeVatrons) are sources theorized to accelerate cosmic rays up in energy. The accelerated expected interact hadronically with nearby ambient gas or the interstellar medium, resulting γ -rays and neutrinos. Recently, Large High Altitude Air Shower Observatory (LHAASO) identified 12 -ray emissions above 100 TeV, making them candidates for PeVatrons. While at these high energies Klein–Nishina effect exponentially suppresses leptonic emission from...
This paper presents the results of a search for neutrinos that are spatially and temporally coincident with 22 unique, non-repeating Fast Radio Bursts (FRBs) one repeating FRB (FRB121102). FRBs rapidly growing class Galactic extragalactic astrophysical objects considered potential source high-energy neutrinos. The IceCube Neutrino Observatory's previous analyses have solely used track events. utilizes seven years IceCube's cascade events which statistically independent event selection allows...
Searching for the sources of high-energy cosmic particles requires sophisticated analysis techniques, frequently involving hypothesis tests with unbinned log-likelihood (LLH) functions. SkyLLH is an open-source, Python-based software tool to build these LLH functions and perform likelihood-ratio tests. We present a new easy-to-use modular extension that allows user neutrino point source searches in entire sky using ten years IceCube public data. To guide user, provides tutorials showing how...