Elusive romance of top-quark pairs observed at the LHC
Prof. Dr. Andrea Knue (University Dortmund)

The top quark is the heaviest elementary particle known to date. With this very large mass come interesting consequences, like its extremely short lifetime. Unlike other quarks, which can form bound states, the top quarks lifetime does not allow for a stable bond. If two top quarks are produced almost at rest however, they can briefly exchange gluons before they then decay individually. This pseudo-bound state was already predicted in 1987, before the top quark was even discovered. It was thought to be impossible to measure this state at the LHC, as it constitutes less than 1% of the total production rate and is difficult to see in the data. With improved analysis techniques and theoretical predictions however, the CMS and ATLAS experiments have recently observed an excess of data close to the production threshold. This presentation will discuss these new measurements and shed some light on the fleeting connection between the two top quarks.