Measurement of the Mass and Width of the W Boson in e+e- Collisions at sqrt{s} = 161 - 209 GeV

TL;DR

This paper reports precise measurements of the W boson mass and width using data from LEP2 collisions, employing direct reconstruction methods across multiple decay channels, with results surpassing previous DELPHI measurements.

Contribution

First comprehensive measurement of W boson mass and width from LEP2 data using direct reconstruction in multiple channels, improving precision over earlier results.

Findings

W boson mass: 80.336 GeV/c^2 with uncertainties

W boson width: 2.404 GeV/c^2 with uncertainties

Results supersede previous DELPHI measurements

Abstract

A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during the full LEP2 programme (1996-2000). The data sample has an integrated luminosity of 660 pb^-1 and was collected over a range of centre-of-mass energies from 161 to 209 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the W+W- -> lvqq and W+W- -> qqqq channels. The W mass result for the combined data set is M_W = 80.336 +/- 0.055 (Stat.) +/- 0.028 (Syst.) +/- 0.025 (FSI) +/- 0.009 (LEP) GeV/c^2, where FSI represents the uncertainty due to final state interaction effects in the qqqq channel, and LEP represents that arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is Gamma_W = 2.404 +/- 0.140 (Stat.) +/- 0.077 (Syst.) +/- 0.065 (FSI) GeV/c^2. These results supersede all values previously published by the DELPHI collaboration. This paper is dedicated to the memory of Carlo Caso.