Stable Heavy Hadrons in ATLAS

Several extensions to the SM feature heavy long-lived particles with masses of O(10^2-10^3 GeV) and mean lifetimes fulfilling $CT \geq 10m$. Among such theories are supersymmetric scenarios as well as extra-dimensional models in which the heavy new particles are seen as Kaluza-Klein excitations of the well-known SM particles. Such particles will, from the point of view of a collider experiment be seen as stable. This thesis is concerned with the case where the exotic heavy particles emph{can} be considered stable while traversing the detector. Specifically the case is considered where the particles in question carry the charge of the strong nuclear force, commonly referred to as emph{colour charge}. A simulation kit has been developed using GEANT4. This framework is the current standard in experimental particle physics for the simulation of interactions of particles with matter, and it is used extensively for detector simulation. The simulation describes the interactions of these particles with matter which is crucial for the discovery and identification of stable massive particles and the understanding of the possible underlying theories predicting them. The simulation is presented and compared to earlier work. It has been incorporated into the simulation software of the ATLAS experiment allowing for the simulation of full events for the varying physics scenarios. An analysis is presented using the simulation software to evaluate the discovery potential for heavy gluon-like objects exemplified by a quasi-stable gluino as the next-lightest supersymmetric particle (NLSP) of split supersymmetry. This analysis is the first analysis for this type of phenomenology to use full simulation as well as trigger simulation. The detailed analysis is then used as a template to comment on the feasibility of observing stable massive particles as they appear in other models. One such model is here exemplified by an extra-dimensional scenario.