Measurement of the Top Quark Mass with an {\em in situ}\ W$\to q\bar{q}\prime$ Calibration at CDF

We present a preliminary measurement of the top quark mass using data from $p\bar{p}$\ collisions at $\sqrt{s} = 1.96$\ TeV collected by the CDF detector. We select $t\bar{t}$\ events where one W boson decays leptonically and the other hadronically. The observed invariant mass of the hadronic W boson decay is used to reduce the largest systematic uncertainty arising from the jet energy scale. The top quark mass and hadronic W boson mass distributions reconstructed in data are compared to Monte Carlo expectations to determine simultaneously the top quark mass and the jet energy scale.