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Register a new userMeasurement of the W Mass at LEP2
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C.J. Parkes
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The mass of the W boson has been measured by the LEP collaborations from the data recorded during the LEP2 programme at e+ e- centre of mass energies from 161 to 209 GeV, giving the result : mw = 80.450 +/- 0.039 GeV/c^2. This paper discusses the measurements of the W Mass from direct reconstruction of the invariant mass of the WW decay products, particular emphasis is placed on the evaluation of systematic errors. Results on the direct measurement of the W width are also presented.
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In the energy region of LEP2 and above, four fermion final states in e+e- collisions can be produced by Feynman diagrams involving two, one or zero resonant bosons...
The $W$ boson mass is measured using proton-proton collision data at $sqrt{s}=13$ TeV corresponding to an integrated luminosity of 1.7 fb$^{-1}$ recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon $q/p_T$ distribution of a sample of $W to mu u$ decays and the $phi^*$ distribution of a sample of $Ztomumu$ decays the $W$ boson mass is determined to be begin{equation*} m_{W} = 80354 pm 23_{rm stat} pm 10_{rm exp} pm 17_{rm theory} pm 9_{rm PDF}~mathrm{MeV}, end{equation*} where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.
In a study of the reaction e-e+ -> W-W+ with the DELPHI detector, the probabilities of the two W particles occurring in the joint polarisation states transverse-transverse (TT), longitudinal-transverse plus transverse-longitudinal (LT) and longitudinal-longitudinal (LL) have been determined using the final states WW -> l nu q qbar (l = e, mu). The two-particle joint polarisation probabilities, i.e. the spin density matrix elements rho_TT, rho_LT, rho_LL, are measured as functions of the W- production angle, theta_W-, at an average reaction energy of 198.2 GeV. Averaged over all cos(theta_W-), the following joint probabilities are obtained: rho_TT = (67 +/- 8)%, rho_LT = (30 +/- 8)%, rho_LL = (3 +/- 7)% . These results are in agreement with the Standard Model predictions of 63.0%, 28.9% and 8.1%, respectively. The related polarisation cross-sections sigma_TT, sigma_LT and sigma_LL are also presented.
We present precision calculations of the processes e+e- -> 4-fermions in which the double resonant W+W- intermediate state occurs. Referring to this latter intermediate state as the signal process, we show that, by using the YFS Monte Carlo event generators YFSWW3-1.14 and KORALW1.42 in an appropriate combination, we achieve a physical precision on the signal process, as isolated with LEP2 MC Workshop cuts, below 0.5 per cent. We stress the full gauge invariance of our calculations and we compare our results with those of other authors where appropriate. In particular, sample Monte Carlo data are explicitly illustrated and compared with the results of the program RacoonWW of Dittmaier {it et al.}. In this way, we show that the total (physical plus technical) precision tag for the WW signal process cross section is 0.4 per cent for 200 GeV, for example. Results are also given for 500 GeV with an eye toward the LC.
We present a measurement of the $W$-boson mass, $M_W$, using data corresponding to 2.2/fb of integrated luminosity collected in ppbar collisions at $sqrt{s}$ = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. The selected sample of 470126 $Wto e u$ candidates and 624708 $Wtomu u$ candidates yields the measurement $M_W = 80387pm 12$ (stat) $pm 15$ (syst)$ = 80387 pm 19$ MeV$/c^2$ . This is the most precise single measurement of the $W$-boson mass to date.
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