Optimal determination of New Physics couplings: A comparative study

Abstract: We study the determination of new physics (NP) parameters using the optimal observable technique (OOT) in situations where the standard model (SM) dominates over the NP effects, and when the NP dominates over the SM contribution, using the 2-Higgs doublet model as an illustrative example; for the case of SM domination we extend our results using an effective theory parameterization of NP effects. For the case of SM dominance we concentrate on $t \bar{t}$ production in an $e<sup>+e<sup>-$ collider, while for the case of NP dominance we consider both $t \bar{t}$ production and pair production of charged scalars, also in an $e<sup>+e<sup>-$ collider. We discuss the effects of the efficiency of background reduction, luminosity and beam polarization, and provide a comparison of the optimal uncertainties with those obtained using a standard $\chi<sup>2$ analysis of (Monte Carlo generated) collider data.