THE MEASUREMENT OF M(W) FROM THE W- THRESHOLD CROSS-SECTION AT LEP2(W)

The rapid increase of the e(+)e(-) --> W+W- cross section in the thres hold region provides a method for measuring M(W) at LEP2. The dependen ce of the theoretical cross section - including the effects of the fin ite W width, Coulomb interactions and initial state radiation - on the collider energy and on the mass and width of the W is investigated in order to deduce the optimal collider energy which maximizes the sensi tivity to M(W). Statistical and systematic uncertainties are studied i n detail. The background contribution from QCD four-jet production is estimated. It is shown that by running LEP2 at root 2 approximate to 1 61 GeV and obtaining a luminosity of order 100 pb(-1) per experiment, an uncertainty on the measured value of M(W) of +/- 70 MeV should be a chievable.