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A search for the production of events containing three W bosons predicted by the standard model is reported. The search is based on a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the CERN LHC and corresponding to a total integrated luminosity of 35.9 fb$^{-1}$. [...]

A search for anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets in proton-proton collisions at $√s$= 13 TeV at the LHC is reported. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ collected with the CMS detector [...]

In the first part of this thesis we investigate the viability of a class of models for de Sitter (dS) vacua in string theory, due to Kachru, Kallosh, Linde and Trivedi (KKLT). We start by explaining why the success or failure of such models is sensitive to a large number of Planck suppressed operators, and collect circumstantial evidence that this UV sensitivity cannot be evaded with delicately engineered models such as the Kallosh-Linde (KL) racetrack due to a generic conflict with the weak gravity conjecture (WGC) for axions. [...]

A search for a light charged Higgs boson (H$^+$) decaying to a W boson and a CP-odd Higgs boson (A) in final states with e$\mu\mu$ or $\mu\mu\mu$ is performed using data from pp collisions at $\sqrt{s}=$ 13 TeV, recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. In this search, it is assumed that the H$^+$ boson is produced in decays of top quarks, and the A boson decays to two oppositely charged muons. [...]

Event-by-event correlations of azimuthal anisotropy Fourier coefficients ($v_n$) in 8.16 TeV pPb collision data, collected by the CMS experiment at the LHC, are extracted using a subevent four-particle cumulant technique. The pseudorapidity range of the CMS tracker from $-$2.4 to 2.4 is divided into either two, three, or four distinct subevent regions. [...]

A search for narrow low-mass resonances decaying to quark-antiquark pairs is presented. The search is based on proton-proton collisions events collected at 13 TeV by the CMS detector at the CERN LHC. [...]

A search for decays of the Higgs and Z boson to pairs of J/$\psi$ or $\Upsilon$(nS) (n=1, 2, 3) mesons, with their subsequent decay to $\mu^+\mu^-$ pairs, is presented. The analysis uses data from proton-proton collisions at $\sqrt{s}=$ 13 TeV, collected with the CMS detector at the LHC in 2017 and corresponding to an integrated luminosity of 37.5 fb$^{-1}$. [...]

A search for vector-like leptons in multilepton final states is presented. The data sample corresponds to an integrated luminosity of 77.4 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016 and 2017. [...]

A search for supersymmetric particles produced in the vector boson fusion topology in proton-proton collisions is presented. The search targets final states with one or zero leptons, large missing transverse momentum, and two jets with a large separation in rapidity. [...]

A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. [...]