Measurement of the W boson mass and width in e+e- collisions at LEP

TL;DR

This paper reports a precise measurement of the W boson mass and width from e+e- collision data at LEP, utilizing a new method to reduce color reconnection effects for improved accuracy.

Contribution

It introduces a novel procedure that excludes low energy particles to minimize color reconnection effects in W mass measurement.

Findings

W boson mass measured as 80.440 GeV/c^2 with high precision.

W boson width determined as 2.14 GeV with associated uncertainties.

The new method improves the reliability of W mass and width measurements.

Abstract

The mass of the W boson is determined from the direct reconstruction of its decays into purely hadronic and semi-leptonic events in e+e- collisions at LEP. The data sample corresponds to an integrated luminosity of 683 inverse picobarns collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new procedure is adopted in which low energy particles are not considered in the mass determination from the purely hadronic channel. The combined result from all channels is Mw = 80.440+-0.043(stat.)+-0.024(syst.)+-0.009(FSI)+-0.009(LEP) GeV/c**2 where FSI represents the possible effects of final state interactions in the purely hadronic channel. From two-parameter fits to the W mass and width, the W width is found to be Gw = 2.14+-0.09(stat.)+-0.04(syst.)+-0.05(FSI)+-0.01(LEP) GeV