Dartmouth Events

Abstract: The large gap between the strengths of weak interactions and gravitation has been a deep concern in recent attempts to unify fundamental interactions. The so-called hierarchy problem originates from the existence of two separate energy scales (Fermi and GUT) on which independent spontaneous symmetry breaking mechanisms should be present. In order to overcome this potential issue, models have been proposed in which gravity at the Fermi scale should be about 32 orders of magnitude stronger than gravity as we observe in the macroscopic world. This 'strong' gravity would have a strength of the same order of the weak interactions, suggesting a strong relationship with potential for their unification. As a consequence of strong gravity, due to an increased Schwarzschild radius, such models generally result in a large increase for the probability of micro black-hole formation in particle collisions. Recently bounds on micro black-hole production have been reported based on high-energy proton-proton collision at the two main  experiments of the Large Hadron Collider at CERN, CMS and ATLAS. However, hadronic collisions do not provide a clean setting to study black-hole formation, and the bounds have been criticized in the literature. This thesis reports evaluations of the probability of micro black-hole formation using electron-electron collision processes, with various analytical approximations and numerical methods. We also evaluate the main sources of background and systematic effects present in purely leptonic high-energy collisions, comparing the case of electrons and muons.