A search for boson that lies beyond the standard model is conducted where the progenitor 125 Gev Higgs Boson decays ultimately to four leptons (electrons or muons). The Higgs boson provides a portal into the hidden sector which contains dark particles. The processes under consideration include H → ZX→ 4l and H → XX → 4l where X is the dark vector boson Zd or the pseudoscalar boson a, which are...
The search for W$^\prime \to tb $ decays in the hadronic final states using the full run 2 data, which was collected by the ATLAS detector at the Large Hadron Collider (LHC), is on going. Reconstruction of the top-quark is one of the crucial steps in this search. To conduct the study of improving the top-quark reconstruction, two signal samples, which had 2 and 3.5 TeV W$^\prime$ masses were...
Improvement in the modelling of color reconnection (CR) is critical for precise measurements in $t\bar{t}$ events at the Large Hadron Collider. Modelling of CR is one of the main sources of uncertainty in top quark measurements. Different experimental observables have been studied, but due to lack of sensitivity they don't provide convenient input to constrain the modelling of CR. In this...
Several ongoing projects, involving data analysis using jet substructure and machine learning method will be summarised. ATLAS boosted heavy neutrino search and the measurement of several substructure observables in different topologies will be mentioned. The former is a precursor of several other planned searched in unusual topologies. Jet tagging using modern machine learning methods is...
