Andrew Leister

Although the Standard Model of Particle Physics has been generally successful in modeling fundamental particles and their interactions, it does not incorporate many observed physical phenomena. Many theoretical models attempting to explain physics beyond the Standard Model have been developed, several of which include one or more additional neutral gauge bosons, or Z’. The potential mass range of a Z’ is quite large and for some models includes Z’ masses at the TeV scale. A search for a TeV-scale resonance of Z’ decaying to tau-antitau pairs is presented. The search is performed using proton-proton collisions with center-of-mass energies of 8 TeV, produced at the Large Hadron Collider. The data was collected by the ATLAS detector in 2012 and corresponds to 19.5-20.3 fb^(-1) of integrated luminosity. The analysis is performed separately across three channels, each corresponding to a particularly decay mode of the tau-antitau pair. The numbers of events in high-mass regions of data are counted and compared to the expectations from Standard Model backgrounds and Z’ Signals. Bayesian 95%-credibility upper limits are placed on the Z’ cross section times ditau branching ratio for each channel and for a combination of the channels. These are used to set limits on the Z’ mass. The Z’ models considered include the Sequential Standard Model (SSM), SSM variations with altered decay widths and couplings to fermions, and the Non-Universal G(221) model with enhanced couplings to third-generation fermions.