The results of the DELPHI experiment on four-fermion production at LEP2 are presented.
The measurement of the cross-section for boson pair production (WW,ZZ) and for single boson processes (Wen) is described. Differential cross-sections can be used to derive information on Triple Gauge Couplings. The main part of the talk is devoted to the precise measurement of the mass of the W boson. The experimental techniques are reviewed.
Emphasis is put on the sources of systematic uncertainty, which currently limit the accuracy of the measurement, and on the possibilities to improve the precision by the end of the LEP2 programme.
