Kinematic Cusps With Two Missing Particles I: Antler Decay Topology

Understand

The kinematics of a final state system with two invisible particles and two visible particles can develop cusped peak structures.

• This happens when the system has a fixed invariant mass (such as from a narrow resonant particle decay or with a fixed collision c.m.
• energy) and undergoes decays of two on-shell intermediate particles.
• Focusing on the "antler decay topology", we derive general analytic expressions for the invariant mass distribution and the kinematic cusp position.