The Top Quark Width at the CDF Experiment

We study a measurement of the total width of the top quark, thus the top quark lifetime, from $p\bar{p}$ collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. In each $t\bar{t}$ event in the lepton+jets final state, the reconstructed top quark invariant mass is determined by minimizing a $\chi^2$ for the overconstrained kinematic system, and the reconstructed mass distribution is formed for the selected event sample. The top quark width is extracted by fitting the reconstructed mass distribution to a template function which incorporates top quark events and expected backgrounds, and varies with the top quark width.