Alexander Grohsjean, 12.05.2020

 

Alexander Grohsjean (DESY)

Top quark spin: A window to new physics?

Abstract:
High precision measurements of the properties of elementary particles are essential to understand the Universe at smallest scales. However, they also might give us exciting insights to the largest scales of the Universe, such as the understanding of Dark Matter, and may provide an avenue to physics beyond the Standard Model (BSM). The analysis of observables with small systematic uncertainties in the phase space region of new physics are of particular interest.
In this talk, the first measurement of the full ttbar spin density matrix at the CMS experiment in proton-proton scattering at the Large Hadron Collider is presented. The general analysis concept and its application in the quest for BSM physics are highlighted. The measurement provides an important answer to an anomaly observed at ATLAS in 2018 and is used to constrain anomalous couplings in an Effective Field Theory framework with greatest sensitivity. It will also be shown how the tt spin density matrix can be utilized to enhance the sensitivity in searches for new scalar particles and how this could shed light on the nature of Dark Matter.

Host: Danilo Meuser