Study of the Higgs boson decaying into invisible particles with simulated events at $\sqrt{s} = \unit{13}{\tera\electronvolt}$ with the ATLAS detector

One of the main purposes of the high-luminosity LHC (HL-LHC) program at CERN will be to study in more detail the Higgs boson and measure its couplings. For the HL-LHC project, the ATLAS detector will have to be upgraded. The mean number of interactions per crossing will be about 200 compared to 40 in Run-2. The ATLAS detector will have to cope with this increased pile-up. In the forward-backward region, there is a proposal to insert a high-ganularity timing detector (HGTD), which could provide a new powerful trigger capability of interesting physics signal such as vector-boson-fusion (VBF) and possibility to separate pile-up from hard scatter signals.\\ In order to evaluate the physics potential of such upgrades, analyses are needed to determine whether the gain from HGTD in terms of geometrical acceptance, improved granularity and jet discrimination based on timing information could increase VBF signal detection efficiency and background rejection. This study is the first milestone towards assessing ultimately the gain brought by the HGTD to the VBF analyses. In the following, the VBF signal efficiency is revisited and optimized further by studying the shapes of kinematic distributions, with datasets corresponding to an integrated luminosity of $\unit{3000}{\femto\reciprocal\barn}$, prior to using the HGTD kinematic information.