Higgs Searches with Bottom Quarks and Invisible Particles

An essential search to answer the question of whether the newly discovered boson of mass 125 GeV at the Large Hadron Collider (LHC) is the standard model Higgs boson ($H$) is the search for decay of the boson into a pair of bottom quarks ($b {\overline{b}}$), as this is theoretically the dominant decay channel of a low-mass Higgs boson. For best signal-to-background sensitivity, the associated production of the Higgs boson with a vector boson ($V$ = $W$ or $Z$) is used. The search is carried out in six channels based on the decay of the vector boson: $W(\mu\nu)H(b {\overline{b}})$, $W(e\nu)H(b {\overline{b}})$, $W(\tau\nu)H(b {\overline{b}})$, $Z(\mu\mu)H(b {\overline{b}})$, $Z(ee)H(b {\overline{b}})$, and $Z(\nu {\overline{\nu}})H(b {\overline{b}})$. This dissertation reports the results of this search, focusing on the details of the analysis for the $Z(\nu {\overline{\nu}})H(b {\overline{b}})$\ channel. A data sample, recorded by the Compact Muon Solenoid (CMS) experiment at the LHC, that corresponds to 18.9 fb$^{-1}$ integrated luminosity at the center-of-mass energy $\sqrt{s} = 8$ TeV is analyzed. The results of this channel is combined with those of the other channels, and with the earlier $\sqrt{s} = 7$ TeV results, to produce the final CMS Run~I results. A mild excess of events is observed above the expected background with a local significance of 2.1 standard deviations. This is compatible with the expectation of 2.1 standard deviations when assuming the production of the standard model Higgs boson signal of mass 125 GeV. The measurements represent the first indication of the $H \to b {\overline{b}}$\ decay at the LHC. These measurements are one of the key components in the global fit of the Higgs couplings and contributed to the CMS Run~I ``legacy'' publication that describes the properties of the discovered Higgs boson.