M.Sc Thesis

M.Sc StudentGalon Iftah
SubjectUnderstanding New Physics at the LHC
DepartmentDepartment of Physics
Supervisor PROF. Yael Shadmi
Full Thesis textFull thesis text - English Version


The Large Hadron Collider at CERN, working at 14TeV center of mass energy, will probe new physics at the TeV scale. The current theory of particle interactions, the standard model (SM), though accurately predicting experimental results, is still inadequate for several reasons. The hierarchy problem, the lack of dark matter candidates and the flavor puzzle are some of the main problems that seem to point to the existence of new physics.

A popular theory for new physics extending the SM is supersymmetry (SUSY). In SUSY theories, each SM particle has a superpartner differing by half a spin unit. SUSY predicts that the mass of a SM particle is equal to that of its superpartners. The fact that superpartners have not been discovered, leads to the conclusion that if SUSY exist, it must be a broken symmetry.

SUSY theories have several advantages, the most important one being that they solve the hierarchy problem. Another advantage of SUSY theories is that they supply candidates for dark matter in the form of weakly interacting stable massive particles

Alongside these advantages, SUSY theories introduce new flavor problems. Since FV processes are extremely well bounded, the flavor structure of SUSY is very constrained. It is for this reason that most studies of SUSY theories have focused on SUSY-breaking schemes which are minimally flavor violating (MFV) - that is, ones in which the Yukawa interactions are the only source of flavor violation.

Recent work concerning the lepton sector has shown that one can go beyond. This has important implications for LHC studies which have mostly concentrated on MFV scenarios. In this work we give an analysis of such lepton flavor violating (LFV) models in which the breaking mechanism is a combination of gauge mediated SUSY breaking and gravity mediated SUSY breaking with an abelian flavor symmetry. These models are characterized by flavor violating couplings and a by a slepton NLSP in large regions of the parameter space. In these cases some of the sleptons are degenerate in mass to some extent. The analysis in this work entails the calculations of all the relevant leptonic decay rates in these LFV models including 2-body and 3-body slepton decays. These calculations have been embedded into a program package, SPICE, which calculates the spectrum and decay rates of generic LFV models which can then be used for simulations .