M_T2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC

TL;DR

This paper introduces a method combining M_T2 and on-shell conditions to reconstruct missing momenta in collider events, aiding in spin measurements of new particles without precise mass knowledge.

Contribution

The paper presents a novel M_T2-assisted on-shell reconstruction scheme for missing momenta, improving spin measurement capabilities at the LHC.

Findings

Reconstructed momenta are well correlated with true WIMP momenta.

Spin determination is feasible without precise mass measurements.

Method enhances analysis of new physics events with invisible particles.

Abstract

We propose a scheme to assign a 4-momentum to each WIMP in new physics event producing a pair of mother particles each of which decays to an invisible weakly interacting massive particle (WIMP) plus some visible particle(s). The transverse components are given by the value that determines the event variable M_T2, while the longitudinal component is determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momentum in general, this M_T2-assisted on-shell reconstruction of missing momenta provides kinematic variables well correlated to the true WIMP momentum, and thus can be useful for an experimental determination of new particle properties. We apply this scheme to some processes to measure the mother particle spin, and find that spin determination is possible even without a good knowledge of the new particle masses.