Supersymmetry (SUSY) introduces superpartners of the Standard Model (SM) particles. If their masses are typically O(100 GeV) ∼ O(TeV), a lightest neutralino can be a candidate for the dark matter, and the problem is solved by canceling the correction of the Higgs boson mass. Further, SUSY can explain the experimental result of the muon magnetic moment (g-2). This book presents a search for electroweakinos—the superpartners of the SM electroweak bosons—such as charginos and neutralinos using data at the LHC collected by the ATLAS detector. Pair-produced electroweakinos decay into the light ones and SM bosons (W/Z/h), and with the large mass difference between the heavy and light electroweakinos, the SM bosons have high momenta. In a fully hadronic final state, quarks decayed from the bosons are collimated, and can consequently be reconstructed as a single large-radius jet. This search has three advantages. The first is a statistical benefit by large branching ratios of the SM bosons. The second is to use characteristic signatures—the mass and substructure—of jets to identify as the SM bosons. The last is a small dependency on the signal model by targeting all the SM bosons. Thanks to them, the sensitivity is significantly improved compared to the previous analyses. Exclusion limits at the 95% confidence level on the heavy electroweakino mass parameter are set as a function of the light electroweakino mass parameter. They are set on wino or higgsino production models with various assumptions, such as the branching ratio of their decaying and the type of lightest SUSY particle. These limits are the most stringent limits. Besides, this book provides the most stringent constraints on SUSY scenarios motivated by the dark matter, the muon g-2 anomaly, and the naturalness.

The Large Hadron Collider, a 7 {circle_plus} 7 TeV proton-proton collider under construction at CERN (the European Laboratory for Particle Physics in Geneva), will take experiments squarely into a new energy domain where mysteries of the electroweak interaction will be unveiled. What marks the 1-TeV scale as an important target? Why is understanding how the electroweak symmetry is hidden important to our conception of the world around us? What expectations do we have for the agent that hides the electroweak symmetry? Why do particle physicists anticipate a great harvest of discoveries within reach of the LHC?

.Studies of the electroweak interactions using final states with leptons in proton-proton collisions at the Large Hadron Collider at [square root of] s = 7 TeV, [square root of] s = 8 TeV, and [square root of] 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 B(W --> lv) 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.

A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6[sigma] deviation in the muon g-2 measurement. We suggest top quark decays as a venue to search for light dark force carriers at the LHC. Such Z's can be easily boosted, and they can decay into highly collimated leptons (lepton-jet) with large branching ratio. We investigate a scenario where a top quark decays to bW accompanied by one or multiple dark force carriers and find that such a scenario could be easily probed at the early stage of LHC Run 2.

A search is performed for the production of a massive W' boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb$^{{u2013}1}$ collected with the CMS detector at the LHC in proton-proton collisions at $ \sqrt{s}=8 $ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W' boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W' boson are obtained, together with constraints on the left-handed and right-handed couplings of the W' boson to quarks. The production of a right-handed W' boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. Furthermore, this mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.