${{\mathit Z}}$ MASS

OUR AVERAGE is given by the weighted average of the combined CDF result and the combined LEP result, assuming no correlations between CDF and LEP. The combined LEP result, $91.1876$ $\pm0.0021$ GeV, is obtained using the fit procedure and correlations as determined by the LEP Electroweak Working Group (see the note “The ${{\mathit Z}}$ boson” and ref. LEP-SLC 2006). The LEP fit is performed using the ${{\mathit Z}}$ mass and width, the ${{\mathit Z}}$ hadronic pole cross section, the ratios of hadronic to leptonic partial widths, and the ${{\mathit Z}}$ pole forward-backward lepton asymmetries. This set is believed to be most free of correlations.

The ${{\mathit Z}}$-boson mass listed here corresponds to the mass parameter in a Breit-Wigner distribution with mass dependent width. The value is 34 MeV greater than the real part of the position of the pole (in the energy-squared plane) in the ${{\mathit Z}}$-boson propagator. Also the LEP experiments have generally assumed a fixed value of the ${{\mathit \gamma}}−{{\mathit Z}}$ interferences term based on the standard model. Keeping this term as free parameter leads to a somewhat larger error on the fitted ${{\mathit Z}}$ mass. See ACCIARRI 2000Q and ABBIENDI 2004G for a detailed investigation of both these issues.
$\bf{ 91.1880 \pm0.0020}$ OUR AVERAGE
$91.1923$ $\pm0.0071$ 1
CDF ${\it{}E}^{\it{}p\overline{\it{}p}}_{\rm{}cm}$= $1.8$ TeV
$91.1876$ $\pm0.0021$ 2
LEP ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
• • We do not use the following data for averages, fits, limits, etc. • •
$91.084$ $\pm0.107$ 3
H1 ${{\mathit e}^{\pm}}{{\mathit p}}$
$91.1872$ $\pm0.0033$ 4
OPAL ${\it{}E}^{\it{}ee}_{\rm{}cm}$= LEP1 + $130 - 209$ GeV
$91.272$ $\pm0.032$ $\pm0.033$ 5
L3 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $183 - 209$ GeV
$91.1852$ $\pm0.0030$ 4.57M 6
OPAL ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$91.1863$ $\pm0.0028$ 4.08M 7
DLPH ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$91.1898$ $\pm0.0031$ 3.96M 8
L3 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$91.1875$ $\pm0.0039$ 3.97M 9
L3 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= LEP1 + $130 - 189$ GeV
$91.1885$ $\pm0.0031$ 4.57M 10
ALEP ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $88 - 94$ GeV
$91.151$ $\pm0.008$ 11
TOPZ ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $57.8$ GeV
$91.74$ $\pm0.28$ $\pm0.93$ 156 12
UA2 ${\it{}E}^{\it{}p\overline{\it{}p}}_{\rm{}cm}$= 630 GeV
$90.9$ $\pm0.3$ $\pm0.2$ 188 13
CDF ${\it{}E}^{\it{}p\overline{\it{}p}}_{\rm{}cm}$= $1.8$ TeV
$91.14$ $\pm0.12$ 480 14
MRK2 ${\it{}E}^{\it{}ee}_{\rm{}cm}$= $89 - 93$ GeV
$93.1$ $\pm1.0$ $\pm3.0$ 24 15
UA1 ${\it{}E}^{\it{}p\overline{\it{}p}}_{\rm{}cm}$= 546,630 GeV
1  AALTONEN 2022 analyse Z decays in the di-muon and di-electron channels using their full Run-II data set. They obtain Z mass values of $91192.0$ $\pm6.4$(stat.)$\pm4.0$(syst.) MeV and $91194.3$ $\pm13.8$(stat.)$\pm7.6$(syst.) MeV, respectively. Combining these results using the systematic uncertainty contributions and their correlations as given in AALTONEN 2022, we obtain an average of $91192.3$ $\pm5.8$(stat.)$\pm4.1$(syst.) MeV.
2  This result combines ABBIENDI 2001A, ABREU 2000F, ACCIARRI 2000C, BARATE 2000C, taking correlated uncertainties into account.
3  ANDREEV 2018A obtain this result in a combined electroweak and QCD analysis using all deep-inelastic ${{\mathit e}^{+}}{{\mathit p}}$ and ${{\mathit e}^{-}}{{\mathit p}}$ neutral current and charged current scattering cross sections published by the H1 Collaboration, including data with longitudinally polarized lepton beams.
4  ABBIENDI 2004G obtain this result using the S$-$matrix formalism for a combined fit to their cross section and asymmetry data at the ${{\mathit Z}}$ peak and their data at $130 - 209$ GeV. The authors have corrected the measurement for the 34 MeV shift with respect to the Breit$-$Wigner fits.
5  ACHARD 2004C select ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit \gamma}}$ events with hard initial$-$state radiation. Z decays to ${{\mathit q}}{{\overline{\mathit q}}}$ and muon pairs are considered. The fit results obtained in the two samples are found consistent to each other and combined considering the uncertainty due to ISR modelling as fully correlated.
6  ABBIENDI 2001A error includes approximately 2.3 MeV due to statistics and 1.8 MeV due to LEP energy uncertainty. This result is included in the LEP average LEP-SLC 2006.
7  The error includes 1.6 MeV due to LEP energy uncertainty. This result is included in the LEP average LEP-SLC 2006.
8  The error includes 1.8 MeV due to LEP energy uncertainty. This result is included in the LEP average LEP-SLC 2006.
9  ACCIARRI 2000Q interpret the $\mathit s$-dependence of the cross sections and lepton forward-backward asymmetries in the framework of the S-matrix formalism. They fit to their cross section and asymmetry data at high energies, using the results of S-matrix fits to ${{\mathit Z}}$-peak data (ACCIARRI 2000C) as constraints. The $130 - 189$ GeV data constrains the ${{\mathit \gamma}}/{{\mathit Z}}$ interference term. The authors have corrected the measurement for the $34.1$ MeV shift with respect to the Breit-Wigner fits. The error contains a contribution of $\pm2.3$ MeV due to the uncertainty on the ${{\mathit \gamma}}{{\mathit Z}}$ interference.
10  BARATE 2000C error includes approximately 2.4 MeV due to statistics, 0.2$~$MeV due to experimental systematics, and 1.7$~$MeV due to LEP energy uncertainty. This result is included in the LEP average LEP-SLC 2006.
11  MIYABAYASHI 1995 combine their low energy total hadronic cross-section measurement with the ACTON 1993D data and perform a fit using an S-matrix formalism. As expected, this result is below the mass values obtained with the standard Breit-Wigner parametrization.
12  Enters fit through ${{\mathit W}}/{{\mathit Z}}$ mass ratio given in the ${{\mathit W}}$ Particle Listings. The ALITTI 1992B systematic error ($\pm0.93$) has two contributions: one ($\pm0.92$) cancels in ${\mathit m}_{{{\mathit W}}}/{\mathit m}_{{{\mathit Z}}}$ and one ($\pm0.12$) is noncancelling. These were added in quadrature.
13  First error of ABE 1989 is combination of statistical and systematic contributions; second is mass scale uncertainty.
14  ABRAMS 1989B uncertainty includes 35 MeV due to the absolute energy measurement.
15  ALBAJAR 1989 result is from a total sample of 33 ${{\mathit Z}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ events.