This letter reports a measurement of the top quark mass, Mtop, in data from collisions at = 1.96 TeV corresponding to 2.7 fb?1 of integrated luminosity at the Fermilab Tevatron using
the CDF II detector. Events with the lepton+jets topology are selected. An unbinned likelihood
is constructed based on the dependence of the lepton transverse momentum, PT, on Mtop. A
maximum likelihood fit to the data yields a measured mass