Electroweak physics and evidence for a Higgs boson decaying to a pair of tau leptons with the CMS detector

Studies of the electroweak interactions using final states with leptons in proton-proton collisions at the Large Hadron Collider at $\sqrt{s}=7$ TeV, $\sqrt{s}=8$ TeV, and $\sqrt{s}=13$ TeV center-of-mass energies are described. Measurements of total inclusive and fiducial $W$ and $Z$ boson production cross sections and their ratios are performed. The $W$ and $Z$ bosons are observed via their decays to electrons and muons. An indirect determination of the total width of the $W$ boson and the $\mathcal{B}(W\rightarrow\ell\nu)$ from the measured cross section ratios is described. The discovery of a new boson with a mass of $125$ GeV at the Large Hadron Collider in $2012$ sheds a new light on understanding the nature of electroweak symmetry breaking. A question of great significance is whether the new field couples to fermions through a Yukawa coupling interaction predicted in the standard model of particles. Evidence of the $125$ GeV Higgs boson decay to a pair of tau leptons with an observed significance of $3.1$ standard deviations is established. The nature of the Higgs sector is probed through searches for neutral resonances decaying to a pair of tau leptons in gluon-fusion and b-quark associated production modes with no observation of a significant excess. In addition, the feasibility of measuring the standard model Higgs boson self-coupling with an expected data sample corresponding to an integrated luminosity of $3000$ fb$^{-1}$ is studied.