Constraining Physics Beyond the Standard Model with Emerging Jets using the ATLAS Experiment

Sammanfattning: Dark matter, the unknown matter that constitutes 85% of all matter in the universe, is one of the greatest mysteries in fundamental physics. One theory that might explain dark matter predicts that there are long-lived particles known as dark pions. If these were created in a particle accelerator, they could decay inside the detector, resulting in particles that seemingly "emerge" from nothing. This phenomenon is known as emerging jets. In this study, emerging jets are simulated with various values of the dark pion average lifetime, dark pion mass, and mediator particle mass. These simulations are compared with a search for displaced vertices conducted by the ATLAS collaboration, allowing one to reinterpret the ATLAS results to constrain the parameter values that the emerging-jets model can have. This study simulates and constrains the allowed values for the dark pion mass, dark pion average life time and mediator mass with 95% confidence level. This is the first study to use results from the ATLAS experiment to constrain the emerging-jets model, as well as the first study to exclude this region of the parameter space.