Using kinematic boundary lines for particle mass measurements and disambiguation in SUSY-like events with missing energy

Understand

We revisit the method of kinematical endpoints for particle mass determination, applied to the popular SUSY decay chain squark -> neutralino -> slepton -> LSP.

• We analyze the uniqueness of the solutions for the mass spectrum in terms of the measured endpoints in the observable invariant mass distributions.
• We provide simple analytical inversion formulas for the masses in terms of the measured endpoints.
• We show that in a sizable portion of the SUSY mass parameter space the solutions always suffer from a two-fold ambiguity, due to the fact that the original relations between the masses and the endpoints are piecewise-defined functions.