Powered by Indico v3.0.3
at 677 0508 2266 （Zoom） ( pwd: 123456 ) https://cern.zoom.us/j/67705082266?pwd=RWx4RjBOUXZ0VFdZbVZvS2ZQcmJqQT09
Abstract:
Supersymmetry(SUSY) is a compelling extension of Standard Model (SM) by introducing a new symmetry relates fermions and bosons. The Minimal Supersymmetric Standard Model (MSSM) introduces a new particle with integer spin for each fermion in SM as its supersymmetry partner. The superpartners for SM bosons are therefore new spin 1/2 particles. These SUSY particles provide a natural solution to the hierarchy problem in SM by cancelling the divergent loop corrections presented in Higgs squared mass calculation. By assuming an ad hoc symmetry called R-parity, the lightest SUSY particle is stable which can be regarded as a suitable candidate for dark matter. If R-parity is not conserved, the violation on baryon number or lepton number is allowed, which can be an explanation to phenomena beyond SM (BSM) such as the observed baryon asymmetry or the neutrino physics.
The Large Hadron Collider offers a great opportunity to search for SUSY particles at TeV scale. I will talk about two searches for SUSY particles that have been conducted with two same-sign leptons or 3 leptons signature in the ATLAS experiment. The first analysis targets the pair production of electroweak gauginos, and the second targets the pair production of strongly-interacting squarks and gluinos. The analysed dataset corresponds to 13 TeV pp collision data collected by ATLAS detector with an integral luminosity of 139 fb-1. No significant excess has been observed over SM predictions. The results are interpreted in the context of different R-parity conserving and R-parity violating SUSY scenarios. Exclusion limits at 95% CL are placed on masses of the superpartners involved in the considered scenarios. Model-independent upper limits on the BSM events that may contribute to the signal regions defined in the analyses are also computed.