A Search for New Physics at the TeV Scale Via a Precise Measurement of the Weak Mixing Angle in Moller Scattering

Abstract

This dissertation reports on a precise measurement of the parity-violating asymmetry in electron-electron (Moeller) scattering at a four-momentum transfer Q{sup 2} = 0.03 (GeV/c){sup 2}. The observed parity-violating asymmetry is A{sub PV} = -128 {+-} 14 (stat.) {+-} 12 (syst.) x 10{sup -9}. This is the most precise asymmetry ever measured in a parity-violating electron scattering. In the context of the Standard Model, the A{sub PV} result determines the weak mixing angle, which is one of the fundamental parameters of the model. The result is sin{sup 2} {theta}{sub W}{sup eff} = 0.2403 {+-} 0.0014, which is consistent with the Standard Model expectation at the current level of precision. The comparison between this measurement of the weak mixing angle at low Q{sup 2} and at the Z{sup 0} pole establishes the running of sin{sup 2} {theta}{sub W} with 6.5{sigma} significance. In addition, they report on the first observation of a transverse asymmetry in electron-electron scattering. The observed asymmetry is A{sub T}{sup Moeller} = 2.7 x 10{sup -6}, which is consistent with the theoretical predictions. They also provide a new measurement of the transverse asymmetry in ep scattering A{sub T}{sup ep} = 2 x 10{sup -6}. The consistency of the result withmore » the theoretical prediction provides new limits on the TeV scale physics. A limit of 0.9 TeV was set on the mass of the extra Z' boson in the SO(10) Model. A limit of 14 TeV and 6 TeV was set on the compositeness scales {Lambda}{sub ee}{sup +} and {Lambda}{sub ee}{sup -}, respectively. Finally a limit of 0.2 TeV was set on ratio of the doubly-charged Higgs mass to the ee{Delta} coupling g{sub ee{Delta}}{sup 2}/m{sub {delta}}{sup 2}.« less