PhD Thesis: Search for Weakly Produced Supersymmetric Particles in the ATLAS Experiment
Friday 14 November 2014
to 16:00 at
Maja Tylmad (Stockholm University, Department of Physics)
The Large Hadron Collider located at CERN is currently the most powerful particle accelerator and ATLAS is an experiment designed to exploit the high energy proton-proton collisions provided by the LHC. It opens a unique window to search for new physics at very high energy, such as supersymmetry, a postulated symmetry between fermions and bosons.
Supersymmetry can provide a solution to the hierarchy problem and a candidate for Dark Matter.
It also predicts the existence of new particles with masses around 1 TeV, thus reachable with the LHC. This thesis presents a new search for supersymmetry in a previously unexplored search channel, namely the production of charginos and neutralinos directly decaying to electroweak onshell gauge bosons, with two leptons, jets, and missing transverse momentum in the final state.
The search is performed with proton-proton collision data at a center of mass energy of √s = 8 TeV recorded with the ATLAS experiment in 2012. The design of a signal region sensitive to the new signal is presented and a data driven technique to estimate the Z+jets background is developed.
Precise measurements of hadronic jet energies are crucial to search for new physics with ATLAS.
A precise energy measurement of hadronic jets requires detailed knowledge of the pulse-shapes from the hadron calorimeter signals. Performance of the ATLAS Tile Calorimeter in this respect is presented using both pion test-beams and proton–proton collision data.