An equal-velocity scenario for hiding dark matter at the LHC

Understand

We consider a light supersymmetric top quark (stop) scenario, where a stop and a neutralino are the lightest supersymmetric particles and the stop mass is close to the sum of the neutralino mass and the top quark mass.

• In this scenario, the top quark and the neutralino coming from the decay of a stop have almost equal velocity vectors, and hence the missing transverse momentum in stop pair production events at colliders is suppressed, which makes the stop search challenging, as in the degenerate scenario where the stop mass and the neutralino mass are nearby.
• In this paper, we propose a novel analysis technique aiming at discovering the stop pair production signal in such an `equal-velocity' scenario.
• The key is to look for events where the missing transverse momentum vector is proportional to the transverse momentum vector of the top quark pair with specific values for the proportionality coefficient, as this coefficient equals to the ratio of the neutralino mass over the top quark mass in the equal-velocity limit.