A possible explanation of mass hierarchy, which is not explained by the Standard Model, is that quarks and leptons are composite objects made of more fundamental particles known as preons.
The existence of preons will be manifest as a four fermion contact
interaction in the annihilation of a quark and anti-quark, in a p-p collision, producing positron-electron pairs. At high mass,
such pairs are also produced from off-shell Z and gamma bosons. This thesis provides a detailed discussion of the analysis strategy to study these processes using the Compact Muon Solenoid
Experiment at the Large Hadron Collider. The study utilizes data recorded in 2012 at sqrt(s) = 8 TeV, corresponding to an integrated luminosity of 19.6 fb-1. The dielectron mass spectrum above
300 GeV shows no significant deviation from the prediction of the Standard Model. In the framework of the left-left iso-scalar model of eeqq contact interactions, 95% CL lower limits on the energy scale parameter are found for destructive (13.1 TeV) and constructive (18.3 TeV) interference between the contact and standard model amplitudes. These limits are the most stringent to date
