Spheres To Jets: Tuning Event Shapes with 5d Simplified Models

TL;DR

This paper introduces a phenomenological approach using simplified extra-dimensional models to generate and analyze intermediate event shapes at the LHC, bridging the gap between jetty and spherical events.

Contribution

It proposes a novel method to produce and understand intermediate event shapes using simplified models in extra dimensions, with an analytic link to model parameters.

Findings

Event isotropy effectively probes spherical event regimes.

Model parameters control the degree of event sphericity.

Analytic understanding of event shape dependence on model parameters.

Abstract

Hidden sectors could give rise to a wide variety of events at the LHC. Confining hidden sectors are known to engender events with a small number of jets when they are weakly-coupled at high energies, and quasi-spherical soft unclustered energy patterns (SUEPs) when they are very strongly-coupled (large 't Hooft coupling) at high energies. The intermediate regime is murky, and could give rise to signals hiding from existing search strategies. While the intermediate coupling regime is not calculable, it is possible to pursue a phenomenological approach in which one creates signals that are intermediate between spherical and jetty. We propose a strategy for generating events of this type using simplified models in extra dimensions. The degree to which the event looks spherical is related to the number of decays produced near kinematic threshold. We provide an analytic understanding of how this is determined by parameters of the model. To quantify the shape of events produced with this model, we use a recently proposed observable---event isotropy---which is a better probe of the spherical regime than earlier event shape observables.