On theoretical uncertainties of the W boson mass measurement at LEP2

We discuss theoretical uncertainties of the measurement of the W boson mass at LEP2 energies, reconstructed with the help of the tandem of the Monte C arlo event generators KoralW and YFSWW3. Exploiting numerical results obtai ned with these programs, and the existing knowledge in the literature, we e stimate that the theoretical uncertainty of the W mass due to electroweak c orrections, as reconstructed at LEP2 with the help of these programs, is si milar to 5 MeV. Since we use certain idealized event selections and a simpl e Mw-fitting procedure, our numerical exercises can be (should be) repeated for the actual "M-W extraction methods" of the LEP2 measurements, using Ko ralW and YFSWW3 or other Monte Carlo programs. (C) 2001 Elsevier Science B. V. All rights reserved,