Measurement of the W mass in e(+)e(-) collisions at 183 GeV

Abstract The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 57 pb −1 collected with the ALEPH detector in 1997 at a centre-of-mass energy of 183 GeV. The invariant mass distributions of reweighted Monte Carlo events are fitted separately to the experimental distributions in the q q q q and all lν q q channels to give the following W masses: m W hadronic =80.461±0.177 (stat.) ±0.045 (syst.) ±0.056 (theory) GeV /c 2 , m W semileptonic =80.326±0.184 (stat.) ±0.040 (syst.) GeV /c 2 , where the theory error represents the possible effects of final state interactions. The combination of these two measurements, including the LEP energy calibration uncertainty, gives m W =80.393±0.128 (stat.) ±0.041 (syst.) ±0.028 (theory) ±0.021 (LEP) GeV /c 2 .