Alp Akpinar: Search For Invisible Decays of the Higgs Boson Produced by Vector Boson Fusion with the CMS Detector

In the Standard Model (SM), the branching fraction of the Higgs boson to invisible final states is precisely predicted to be around 0.1%, through the decay channel to two Z bosons, and each Z boson decaying into a neutrino-antineutrino pair. However, in many Beyond the Standard Model (BSM) scenarios, the Higgs boson acts as a scalar mediator between SM and dark matter particles. In scenarios like these, the branching fraction for the invisible decays of the Higgs boson can be significantly enhanced. Such invisible decays of the Higgs boson can be searched by targeting events in which a Higgs boson is produced via gluon-gluon fusion (ggH), vector boson associated production (VH), or through vector boson fusion (VBF). The events in which the Higgs boson is produced with two jets via VBF will have a unique signature, resulting in two final state jets with large invariant mass and psuedorapidity separation, together with high missing transverse momentum due to the recoil of the invisible particles from the dijet system. This unique signature leads to the rejection of most SM backgrounds, making the VBF channel the most sensitive mode for the invisible decays of the Higgs boson. In this seminar, I will go over the analysis methodology and results for the search of invisible decays of the Higgs boson, produced through the VBF process, using the proton-proton collision data collected within the Run 2 data taking period. I will outline the methods used to suppress detector noise during the analysis, and how these methods are deployed to the online data taking software of the experiment for Run 3 data taking. Finally, I will briefly mention the Phase-2 upgrade plan of the CMS detector and my work related to the tracker system update.