Reconstructing particle masses in events with displaced vertices

TL;DR

This paper introduces a method to determine particle masses in events with displaced vertices, utilizing decay positions and kinematic constraints, applicable to LHC searches for long-lived particles.

Contribution

It presents a novel, event-by-event technique to reconstruct parent and daughter particle masses using displaced vertex information and on-shell conditions.

Findings

Method validated with simulations including detector effects.

Applicable to LHC searches for long-lived particles.

Enables mass reconstruction in events with displaced decays.

Abstract

We propose a simple way to extract particle masses given a displaced vertex signature in event topologies where two long-lived mother particles decay to visible particles and an invisible daughter. The mother could be either charged or neutral and the neutral daughter could correspond to a dark matter particle in different models. The method allows to extract the parent and daughter masses by using on-shell conditions and energy-momentum conservation, in addition to the displaced decay positions of the parents, which allows to solve the kinematic equations fully on an event-by-event basis. We show the validity of the method by means of simulations including detector effects. If displaced events are seen in discovery searches at the Large Hadron Collider (LHC), this technique can be applied.