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| CMS-PAS-SMP-18-014 | ||
| Precision measurement of the Z invisible width with the CMS experiment in pp collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| July 2021 | ||
| Abstract: A direct measurement of the invisible width of the Z boson in proton-proton collisions at a center-of-mass energy of 13 TeV is presented using data recorded by the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3 fb$^{-1}$. The result is extracted from a simultaneous fit to data regions containing predominantly Z boson decay to invisible particles and those dominated by Z boson decay to electron and muon pairs. The invisible width is measured to be 523 $\pm$ 3 (stat) $\pm$ 16 MeV. This result is the first measurement of the Z invisible width at a hadron collider and is the single most precise direct measurement in the world, competitive with the combined direct measurement from the LEP experiments. | ||
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These preliminary results are superseded in this paper, PLB 842 (2023) 137563. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Distribution of ${{p_{\mathrm {T}}} ^\text {miss}}$ for the ${p_\text {T}^{\text {miss}}}$+jets and ${{\mathrm {Z}} /\gamma* \rightarrow \ell\ell}$ regions. The selected muons and electrons are not included in the ${{p_{\mathrm {T}}} ^\text {miss}}$ calculation. The ratio is taken with respect to the SM postfit and includes the prefit result. The residuals are the difference between the data and the SM postfit results, normalized by their uncertainties summed in quadrature. |
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Figure 2:
Measurement of the Z invisible width compared to the direct measurements from the LEP experiments and their combination. |
| Summary |
| In summary, this note presents the first measurement of the Z invisible width at a hadron collider. The measurement is performed using pp collisions at $\sqrt{s} = $ 13 TeV and data corresponding to an integrated luminosity of 36.3 fb$^{-1}$, yielding a result of 523 $\pm$ 3 (stat) $\pm$ 16 (syst) MeV. It represents the single most precise direct measurement of the Z invisible width in the world and is competitive with the combined direct measurement from LEP. |
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