Nonrelativistic Quark Model Calculation of the S parameter

A critical review is presented of the attempts to estimate the Strong Interactions contributions to the parameter $S$ ($L_{10}$ in the QCD Chiral Version). In particular it is discussed why the estimations done for Technicolor are unreliable. $S$ is calculated for heavy doublets of Techniquarks using the Nonrelativistic Quark Model and keeping $v\simeq 0.25$ TeV fixed. It is found that heavy Techniquarks decouple, so it is possible to obtain values for $S$ in agreement with present experimental data.