Probes of New Physics Signatures of new particles in extreme objects and ground-based experiments
by
FB42
AlbaNova Main Building
Abstract
The Standard Model (SM) of particle physics is one of the greatest successes of the 20th century. It offers a beautiful description of the elementary par- ticles and their interactions based on symmetries and the breaking of them. Despite its success, the SM is regarded as incomplete both because it does not explain certain observed phenomena and because it exhibits fine-tuning prob- lems. This thesis explores how particles beyond the SM (BSM) interact with SM particles, and the signals we should expect from them. In particular, the classes of hypothetical, new particles denoted as "Weakly Interacting Massive Particles" (WIMPs) and "Axion-like Particles" (ALPs) are studied.
This thesis consists of three papers, which all contribute to the search for new particles beyond the SM in different ways. The first paper focuses on a class of WIMPs called "inelastic DM" in which the DM particle must transfer onto a higher-mass state when it scatters off SM particles. In this paper, we have studied whether such a model can explain the discrepancy between the claimed DM signal in DAMA and the lack of one in other direct detection experiments. The second paper of this thesis focuses on ALPs and their signals in the γ-ray spectra of distant sources. ALPs and photons can oscillate in the presence of external magnetic fields, such as the ones that are expected to be present in the jets of blazars (active galactic nuclei). These oscillations should lead to an increased flux in the TeV spectra of these sources. In this paper we used data from the HAWC observatory to study whether the observed γ-ray spectra of these sources were in conflict with the expected spectra for different ALP models.
The last paper in this thesis does not involve any new particles beyond the SM, but investigates whether current models of the isotropic gamma-ray back- ground (IGRB) is consistent with observations. Since searches for new par- ticles depend heavily on our understanding of astrophysical phenomena and the SM processes that take place, studies of these are important. The IGRB consists of all the diffuse γ-ray emission that cannot be assigned to individ- ual point sources. In this paper, we calculated the expected contribution to the IGRB from resolved blazars and found that this introduces an emerging tension between blazar models and observations.
