|M.Sc Student||Yoav Afik|
|Subject||Search for Dark Matter production in nal states with|
two leptons, b-jets and missing transverse
momentum in root s= 13TeV proton- proton
collisions using .....
|Department||Department of Physics||Supervisor||Full Professor Rozen Yoram|
|Full Thesis text|
The existence of dark matter is supported by many astrophysical observations. It has to be stable, heavy, and does not participate in the strong and electro-magnetic interactions. Therefore, it has to be an extension to the standard model of particle physics, and to introduce new particles and interactions within a hidden dark sector.
Simplified models for dark matter assume this kind of extension, where the dark matter and the standard model particles are mediated by a spin-0 particle. The results of a search for new phenomena of dark matter in association with pair are reported, using 13.3 fb-1 of integrated luminosity from LHC proton-proton collisions at Ös = 13 TeV collected by the ATLAS detector. Events with large missing transverse momentum with two charged leptons (electrons or muons) are selected when produced in association with high-momentum jets of which one or more are identified as jets originating from b-quarks. Data driven estimation techniques are used for the main standard model processes background events. The data was found to be consistent with the standard model expectations and exclusion limits at 95% confidence level are derived, assuming the mediator is either a scalar or a pseudo-scalar type particle, and the dark matter is a Dirac fermion. Mediator lighter than 330 GeV is excluded for a maximum coupling strength of the perturbative limit and a dark matter particle mass below 20 GeV.