Abstract:

LHC searches for new physics focus on combinations of hard physics objects. In this talk I will we discuss a qualitatively different soft signal for new physics at the LHC - the "anomalous underlying event". Every hard LHC event will be accompanied by a soft underlying event due to QCD and pile-up effects. Though it is often used for QCD and monte carlo studies, I will propose the incorporation of an underlying event analysis in some searches for new physics. An excess of anomalous underlying events may be a smoking-gun signal for particular new physics scenarios involving new strong forces such as "quirks" in which large amounts of energy may be emitted by a large multiplicity of soft particles. Such new strong dynamics are suggested by models of folded supersymmetry, a new approach to the hierarchy problem. Possible search strategies for such soft diffuse signals in the tracking system and calorimetry of the LHC experiments will be discussed.