Phenomenology of Sarks and Dileptons

We have studied three extensions of the standard model; the sark model, the vector quark model and the 331 model. The sark model has a gauge group SU(2) _{X}otimes SU(3)_{C} otimes SU(2)_{S}otimes U(1) _{Q}, where all gauge symmetries are unbroken. The vector-quark model contains an extra vector-like quark doublet. Finally, the 331 model has a gauge group SU(3)_{C}otimes SU(3)_{L}otimes U(1)_{X } where SU(3)otimes U(1)_ {X} contains the standard electroweak group SU(2)_{L}otimes U(1) _{Y}. This model contains three extended fermion families with the third family treated differently and additional vector gauge bosons. In the sark model, the number of quark-lepton families is constrained to three by the asymptotic freedom for the SU(2)_{X} group. Further, quantization of the electric charge is achieved by the anomaly cancellation conditions. Neutral sark baryons, called narks, are candidates for the cosmological dark matter having the characteristics designed for WIMPS. Further phenomenological implications of sarks are analyzed including electron-positron annihilation, Z^{0 } decay, flavor-changing neutral currents, baryon-number non-conservation, sarkonium and the neutron electric dipole moment. Next, we have studied the CP violation parameter Re(epsilon^'/epsilon) in the vector-quark model and also in the 331 model. For a given value of m_{t}, the vector quark model tends to reduce Re(epsilon ^'/epsilon) whereas the 331 model tends to increase it. If m_{t } is discovered around 150 GeV and the lower experimental value for Re(epsilon^ '/epsilon) (0.74+/- 0.60times 10^{-3}, Fermilab) is confirmed, the standard model is acceptable. But, if its higher value (2.3+/- 0.65times 10 ^{-3}, CERN) persists, a dynamics like the 331 model seems to be favored. Lastly, we have looked for the signatures of the dileptons in e^-p and e ^-e^+ colliders. At HERA, with the center-of-mass energy 314 GeV, a dilepton mass above 150 GeV is inaccessible but at LEPII-LHC, with a 1790 GeV center -of-mass energy, masses up to 650 GeV can be discovered. In an e^+e^- collider, the dileptons with masses up to 180, 450 and 950 GeV may be detected for 200, 500 and 1000 GeV center-of-mass energies, respectively.