Measurement prospects for VBF $H{\rightarrow\,}WW^{(\ast)}{\rightarrow\,}e\nu\mu\nu$ production with 3 $\textrm{ab}^{-1}$ of HL-LHC $pp$-collisions

This note presents the prospects for the ATLAS experiment to observe and measure Vector Boson Fusion (VBF) Higgs-boson production, with the Higgs boson decaying into two $W$ bosons in the High Luminosity LHC environment. The production of two forward jets in association with the Higgs boson, as well as the requirement that the $W$ bosons both decay to leptons, provides a distinctive detector signature. The VBF production process has the second largest Higgs-boson production cross-section at the LHC and can be computed with small theoretical uncertainties. These properties allow for precision measurements in the High Luminosity LHC with 3 $\textrm{ab}^{-1}$ of data. In addition, measurements of the VBF $H{\rightarrow\,}WW^{(\ast)}{\rightarrow\,}e\nu\mu\nu$ process are sensitive to the reconstruction performance of its final-state features including missing transverse energy, leptons, and forward jets, and the reconstruction performance changes with the design of the upgraded ATLAS detector. The projected precision of the VBF Higgs-boson cross-section is shown for three upgrade detector scenarios, of which the "Reference" detector scenario is now the chosen baseline. The measurement precision on the production cross-section in the ``Reference'' detector scenario is about a factor of two better than in the ``Low'' detector scenario.