Mass Determination in SUSY-like Events with Missing Energy

TL;DR

This paper introduces a kinematic method to determine the mass scale of SUSY-like events with missing energy at hadron colliders, achieving high precision even with realistic uncertainties.

Contribution

The paper presents a novel kinematic approach that uses all event information and mass-shell constraints to accurately measure particle masses in SUSY-like decay chains.

Findings

Mass errors range from 4 GeV to 13 GeV depending on event count.

Mass difference errors are significantly smaller.

Method remains effective with realistic momentum uncertainties.

Abstract

We describe a kinematic method which is capable of determining the overall mass scale in SUSY-like events at a hadron collider with two missing (dark matter) particles. We focus on the kinematic topology in which a pair of identical particles is produced with each decaying to two leptons and an invisible particle (schematically, $pp\to YY+jets$ followed by each $Y$ decaying via $Y\to \ell X\to \ell\ell'N$ where $N$ is invisible). This topology arises in many SUSY processes such as squark and gluino production and decay, not to mention $t\anti t$ di-lepton decays. In the example where the final state leptons are all muons, our errors on the masses of the particles $Y$, $X$ and $N$ in the decay chain range from 4 GeV for 2000 events after cuts to 13 GeV for 400 events after cuts. Errors for mass differences are much smaller. Our ability to determine masses comes from considering all the kinematic information in the event, including the missing momentum, in conjunction with the quadratic constraints that arise from the $Y$, $X$ and $N$ mass-shell conditions. Realistic missing momentum and lepton momenta uncertainties are included in the analysis.