arXiv subjects

Maximilian Meier

Publications and source records attributed to Maximilian Meier.

7 recordsLinked to original sources

arXiv2026

Ultrahigh-energy cosmogenic neutrino emissions in the high-redshift universe

The James Webb Space Telescope (JWST) revealed a large population of active galactic nuclei (AGN) with redshifts greater than five. We show that if they emit ultrahigh-energy protons with energies up to $\lesssim 10^{19}$ eV, the cosmogenic neutrino production in the high-redshift CMB field yields a neutrino flux with a bump at around 50 PeV. This flux is potentially consistent with the current neutrino intensity estimate by the IceCube Neutrino Observatory within the parameter space allowed from the AGN luminosity and number density estimates by JWST. Future neutrino observations that confirm the 50-PeV bump and constrain the small-scale anisotropy will infer ultra-high energy cosmic-ray emissions in the early universe.

astro-ph.HE↗

arXiv2025

A search for extremely-high-energy neutrinos with IceCube and implications for the ultra-high-energy cosmic-ray proton fraction

When ultra-high-energy cosmic rays (UHECRs) interact with ambient photon backgrounds, a flux of extremely-high-energy (EHE), so-called cosmogenic, neutrinos is produced. The observation of these neutrinos with IceCube can probe the nature of UHECRs. We present a search for EHE neutrinos using $12.6 \, \mathrm{years}$ of IceCube data. The non-observation of neutrinos with energies $\gtrsim 10 \, \mathrm{PeV}$ constrains the all-flavor neutrino flux at $1 \, \mathrm{EeV}$ to be below $E^2 \Phi_{\nu_e + \nu_\mu + \nu_\tau} \simeq 10^{-8} \, \mathrm{GeV} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1} \, \mathrm{sr}^{-1}$, the most stringent limit to date. This constrains the proton fraction in UHECRs of energy above $30 \, \mathrm{EeV}$ to be $\lesssim 70\%$ if the evolution of the UHECR sources is similar to the star formation rate. Our analysis circumvents uncertainties associated with hadronic interaction models in studies of UHECR air showers, which also suggest a heavy composition at such energies.

astro-ph.HE↗

arXiv2024

Cs-O$_2$-Li as enhanced NEA surface layer with increased lifetime for GaAs photocathodes

GaAs-based photocathodes are the only viable source capable of providing spin-polarized electrons for accelerator applications. This type of photocathode requires a thin surface layer, in order to achieve negative electron affinity (NEA) for efficient photo-emission. However, this layer is vulnerable to environmental and operational effects, leading to a decay of the quantum efficiency $\eta$ characterized by a decay constant or lifetime $\tau$. In order to increase $\tau$, additional agents can be introduced during the activation procedure to improve the chemical robustness of the surface layer. This paper presents the results of recent research on Li as enhancement agent for photocathode activation using Cs and O$_2$, forming Cs-O$_2$-Li as enhanced NEA layer. Measurements yielded an increase in lifetime by a factor of up to 19 $\pm$ 2 and an increase in extracted charge by a factor of up to 16.5 $\pm$ 2.4, without significant reduction of $\eta$. This performance is equal to or better than that reported for other enhanced NEA layers so far.

physics.acc-ph↗

arXiv2024

Recent cosmogenic neutrino search results with IceCube and prospects with IceCube-Gen2

Neutrinos with energies beyond PeV (extremely high energy, EHE) are produced in interaction of the highest energy cosmic rays. One contribution to the EHE neutrino flux is expected to arise from so-called cosmogenic neutrinos generated in ultra high energy cosmic ray interactions with cosmic microwave background photons. Observation of cosmogenic neutrinos can probe the nature of cosmic rays beyond the energies for resonant photo-pion production (GZK cutoff). The IceCube detector instruments a cubic kilometer of the South Pole ice to detect Cherenkov light emitted by charged particles produced in neutrino interactions. In the future IceCube-Gen2 will increase the effective detection volume for EHE neutrinos by adding radio antennas to the in-ice detector. In this contribution we present new constraints on the EHE neutrino flux above $5 \times 10^6$ GeV using 12.6 years of IceCube data. The differential upper limit constrains the all-flavor EHE neutrino flux at 1 EeV to below a level of $E^2 \Phi \sim 10^{-8} \, \mathrm{GeV} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1} \, \mathrm{sr}^{-1}$. Additionally, we also describe the projected sensitivity of the IceCube-Gen2 radio array, which will reach fluxes about 1.5 orders of magnitude smaller than the current limits at 1 EeV.

astro-ph.HE↗

arXiv2023

Search for Extremely High Energy Neutrinos with IceCube

Extremely high energy (EHE) neutrinos (with energies above $10^7$ GeV) are produced in interactions of the highest energy cosmic rays. A primary contribution to the EHE neutrino flux is expected from so-called cosmogenic neutrinos produced when ultra high energy cosmic rays interact with ambient photon backgrounds. Observations of these EHE neutrinos with IceCube can probe the nature of cosmic rays beyond the energies for resonant photo-pion production (GZK cutoff). We present a new event selection of extremely high energy neutrinos by more effectively identifying and rejecting high multiplicity muon bundles with respect to previous analyses. Furthermore, we show the expected improvements of the quasi-differential upper limits on the EHE neutrino flux using 12 years of IceCube data.

astro-ph.HE↗

arXiv2019

Search for Astrophysical Tau Neutrinos with an Improved Double Pulse Method

Tau neutrino identification with the IceCube experiment would open new windows to neutrino physics as well as enable novel searches for cosmic neutrino sources. This work aims at a identification of tau neutrinos with astrophysical origin at energies above 100TeV. For identification, we search for a double pulse structure in the signal of one of IceCubes Digital Optical Modules originating from a tau neutrino interaction and a subsequent tau decay within the detector. In this work, we present constraints on the tau neutrino flux based on an event sample with a livetime of about 7.5 years of IceCube data.

astro-ph.HE↗

arXiv2018

Recent Improvements for the Lepton Propagator PROPOSAL

The lepton propagator PROPOSAL is a Monte-Carlo Simulation library written in C++, propagating high energy muons and other charged particles through large distances of media. In this article, a restructuring of the code is described, which yields a performance improvement of up to $30\,\%$. For an improved accuracy of the propagation processes, more exact calculations of the leptonic and hadronic decay process and more precise parametrizations for the interaction cross sections are now available. The new modular structure allows a more flexible and custom usage, which is further facilitated with a python interface.

hep-ph↗