  We present a measurement of the top quark mass with the Matrix Element method
in the lepton+jets final state. As the energy scale for calorimeter jets
represents the dominant source of systematic uncertainty, the Matrix Element
likelihood is extended by an additional parameter, which is defined as a global
multiplicative factor applied to the standard energy scale. The top quark mass
is obtained from a fit that yields the combined statistical and systematic jet
energy scale uncertainty. Using a data set of 370 pb-1 taken with the D0
experiment at Run II of the Fermilab Tevatron Collider, the mass of the top
quark is measured using topological information to be: mtop(topo) = 169.2
+5.0-7.4 (stat.+JES) +1.5-1.4 (syst.) GeV, and when information about
identified $b$ jets is included: mtop(b-tag) = 170.3 +4.1-4.5 (stat.+JES)
+1.2-1.8 (syst.) GeV. The measurements yield a jet energy scale consistent with
the reference scale.
