Aspects of astrophysical particle production and beyond the Standard Model phenomenology

TL;DR

This thesis explores beyond Standard Model physics at colliders and neutrino astronomy, presenting models tested against data and analyzing neutrino sources, with implications for future constraints in astrophysics and particle physics.

Contribution

It introduces a supersymmetry model explaining collider excesses and evaluates its viability with recent data, alongside novel analyses of neutrino sources and constraints in astrophysics.

Findings

The supersymmetry model explaining the 2015 ATLAS excess is now ruled out by new data.

Obscured matter sources can produce neutrinos detectable by IceCube without conflicting with gamma-ray bounds.

Current constraints on neutrino emission from black hole mergers are weak but will improve soon.

Abstract

This PhD thesis deals with various aspects of (astro)particle physics phenomenology and consists out of two parts: beyond the Standard Model physics and neutrino astronomy. In the first part, I focus on beyond the Standard Model physics at the Large Hadron collider. Concretely, I discuss the interpretation of a 2015 excess seen by ATLAS in events with jets, missing transverse momentum and 2 same-flavour, opposite-charge leptons within a model of gauge-mediated supersymmetry breaking. Our model, which features supersymmetry breaking in multiple hidden sectors, was able to explain the 2015 data because of the appearance of an additional massive neutral particle at the bottom of the spectrum, with couplings dictated by supersymmetry. However, using more recent data, I show that this specific implementation of the model is now ruled out. In the second part, I focus on astroparticle physics and neutrino astronomy. This part consists of two projects. The first and largest of these investigates the possibility that the neutrinos seen by IceCube are produced by sources obscured by matter. We show that, in this case, existing bounds from the extragalactic gamma-ray background can be evaded. In addition, we apply our model to a set of sources selected for possible obscuration and obtain relevant bounds on the parameter space. In the final project, I investigate current constraints on neutrino emission from binary black hole mergers. While no such neutrinos are typically expected, current constraints are not yet able to rule out a substantial contribution of such events to the astrophysical neutrino flux. I show that in the near future, this possibility will be constrained. Both parts are preceded by an extensive introduction and review of their respective fields, written to be of general interest.