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

Understand

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.