Invisible dark gauge boson search in top decays using a kinematic method

Understand

We discuss the discovery potential of a dark force carrier ($Z'$) of very light mass, $m_{Z'} \lesssim {\cal O}(1-10)$ GeV, at hadron colliders via rare top quark decays, especially when it decays invisibly in typical search schemes.

• We emphasize that the top sector is promising for the discovery of new particles because top quark pairs are copiously produced at the Large Hadron Collider.
• The signal process is initiated by a rare top decay into a bottom quark and a charged Higgs boson ($H^\pm$) decaying subsequently into a $W$ and one or multiple $Z'$s.
• The light $Z'$ can be invisible in collider searches in various scenarios, and it would be hard to distinguish the relevant collider signature from the regular $t\bar{t}$ process in the Standard Model.