A search for the lightest supersymmetric partner of the top quark, stop1, produced in ppbar collisions at \sqrt{s}=1.96 TeV has been performed using the DO detector at the Fermilab Tevatron collider. % Assuming the decay blsnu is dominant, leads to a final state with missing energy, an electron and a muon. A good agreement with standard model expectation has been observed in a dataset corresponding to an integrated luminosity of 1.1 fb-1. New limits at 95% confidence level in the plane (mstop1,msneutrino) have been set.