"Probing neutrino lifetime using high-energy astrophysical neutrinos"
Mauricio Bustamante (Physics)
In theories beyond the Standard Model, neutrinos may be unstable and decay with rates that have detectable effects. The cumulative effect of decay on a neutrino flux will be larger the longer the neutrino travel time, or baseline. Therefore, the high-energy (10 TeV -- 2 PeV) astrophysical neutrinos recently discovered by IceCube --- with estimated baselines from several megaparsecs to a few gigaparsecs --- are fertile ground to test decay. I will show how decay distorts the flavor composition of these neutrinos and the rate of neutrino-induced showers. Using these observables, existing and near-future IceCube data improve the lifetime bounds by several orders of magnitude, in the normal and inverted neutrino mass hierarchy.
"Introducing Agnostic Spectral Stacking as a Powerful Method to detect and characterise Weak QSO Absorber Populations"
Stephan Frank (Astronomy)
We have developed a new spectral stacking method that allows for the detection and characterisation of absorber populations that are individually too weak to be detected by traditional line search methods. I will demonstrate how this technique works for the specific case of searching for signatures of NeVIII absorbers, thought to arise in warm to hot circumgalactic gas, at intermediate redshifts (z=0.7-1.2) in an ensemble of high-quality COS-spectra.