MTN is all you need: Production of multiple semi-invisible resonances at hadron colliders

The stransverse mass variable [Formula: see text] was originally proposed for the study of hadron collider events in which [Formula: see text] parent particles are produced and then decay semi-invisibly. Here we consider the generalization to the case of [Formula: see text] semi-invisibly decaying parent particles. We introduce the corresponding class of kinematic variables [Formula: see text] and illustrate their mathematical properties. Many of the celebrated features of the [Formula: see text] kinematic endpoint are retained in this more general case, including the ability to measure the mass of the invisible daughter particle from the stransverse mass kink. We describe and validate a numerical procedure for computing [Formula: see text] in practice. We also identify the configurations of visible momenta which result in nontrivial ([Formula: see text]) values, and derive a pure phase-space estimate for the fraction of such events for any N.