Measurement of Mass and Width of the W Boson at LEP

TL;DR

This paper reports precise measurements of the W boson's mass and decay width using data from LEP, providing important tests of the Standard Model and constraints on new physics.

Contribution

First measurement of W boson mass and width at LEP energies combining multiple final states with high precision.

Findings

W boson mass measured as 80.61 GeV

W boson width measured as 1.97 GeV

Results agree with Standard Model predictions

Abstract

We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in $\mathrm{e^+e^-}$ interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 76.7 pb$^{-1}$. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined to be $\mathrm{M_W}=80.61\pm0.15$ GeV and $\Gamma_{\mathrm{W}}=1.97\pm0.38$ GeV, respectively.