Using Energy Peaks to Measure New Particle Masses

Understand

We discussed in arXiv:1209.0772 that the laboratory frame distribution of the energy of a massless particle from a two-body decay at a hadron collider has a peak whose location is identical to the value of this daughter's (fixed) energy in the rest frame of the corresponding mother particle.

• For that result to hold we assumed that the mother is unpolarized and has a generic boost distribution in the laboratory frame.
• In this work we discuss how this observation can be applied for determination of masses of new particles, without requiring a full reconstruction of their decay chains or information about the rest of the event.
• We focus on a two-step cascade decay of a massive particle that has one invisible particle in the final state: C -> Bb -> Aab, where C, B and A are new particles of which A is invisible and a, b are visible particles.