The LHC experiments have measured the branching fraction for Z decays to four leptons (electrons or muons). We have combined these measurements with the result B(Z → 4 ) = (4.58 ± 0.26) × 10 −6 , allowing a precise comparison to the standard model prediction of (4.70 ± 0.03) × 10 −6 . We use a minimal extension of the standard model to demonstrate that this combined value may be used to set stringent limits on new physics.

A : Minimal spanning trees (MSTs) have been used in cosmology and astronomy to distinguish distributions of points in a multi-dimensional space. They are essentially unknown in particle physics, however. We briefly define MSTs and illustrate their properties through a series of examples. We show how they might be applied to study a typical event sample from a collider experiment and conclude that MSTs may prove useful in distinguishing different classes of events. K: Analysis and statistical methods; Pattern recognition, cluster finding, calibration and fitting methods A X P : 1608.04772