154 research outputs found
Probing neutrino production in high-energy astrophysical neutrino sources with the Glashow Resonance
The flavor composition of high-energy neutrinos carries important information
about their birth. However, the two most common production scenarios,
(hadronuclear) and (photohadronic) processes, lead to the same flavor
ratios when neutrinos and antineutrinos cannot be distinguished. The Glashow
resonant interaction becomes a window to
differentiate the antineutrino contribution from the total diffuse neutrino
flux, thus lifting this degeneracy. We examine the power of Glashow resonant
events in measuring the fraction of the flux with current IceCube
data, and produce projected sensitivities based on the combined exposure of
planned Cherenkov neutrino telescopes around the globe. We find that and
can be distinguished at a 2 significance level in the next
decades, in both an event-wise analysis and a more conservative statistical
analysis, even with pessimistic assumptions on the spectral index of the
astrophysical flux. Finally, we consider the sensitivity of future experiments
to mixed production mechanisms.Comment: 15 pages, 9 figure
Search for TeV Neutrinos from Seyfert Galaxies in the Southern Sky using Starting Track Events in IceCube
Supermassive black holes (SMBHs) power active galactic nuclei (AGN). The
vicinity of the SMBH has long been proposed as the potential site of particle
acceleration and neutrino production. Recently, IceCube reported evidence of
neutrino emission from the Seyfert II galaxy NGC 1068. The absence of a
matching flux of TeV gamma rays suggests that neutrinos are produced where
gamma rays can efficiently get attenuated, for example, in the hot coronal
environment near the SMBH at the core of the AGN. Here, we select the
intrinsically brightest (in X-ray) Seyfert galaxies in the Southern Sky from
the BAT AGN Spectroscopic Survey (BASS) and search for associated neutrinos
using starting track events in IceCube. In addition to the standard power law
flux assumption, we leverage a dedicated disc-corona model of neutrino
production in such an environment to improve the discovery potential of the
search. In this contribution, we report on the expected performance of our
searches for neutrinos from these Seyfert galaxies.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC2023).
See arXiv:2307.13047 for all IceCube contribution
New bounds on light millicharged particles from the tip of the red-giant branch
Stellar energy loss is a sensitive probe of light, weakly coupled dark
sectors, including ones containing millicharged particles (MCPs). The emission
of MCPs can affect stellar evolution, and therefore can alter the observed
properties of stellar populations. In this work, we improve upon the accuracy
of existing stellar limits on MCPs by self-consistently modelling (1) the MCP
emission rate, accounting for all relevant in-medium effects and production
channels, and (2) the evolution of stellar interiors (including backreactions
from MCP emission) using the MESA stellar evolution code. We find MCP emission
leads to significant brightening of the tip of the red-giant branch. Based on
photometric observations of 15 globular clusters whose bolometric magnitudes
are inferred using parallaxes from Gaia astrometry, we obtain robust bounds on
the existence of MCPs with masses below 100 keV.Comment: 12 pages, 8 figure
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