Semi-visible jets + X: Illuminating Dark Showers with Radiation

TL;DR

This paper explores how initial-state radiation can enhance the detection of semi-visible jets at the LHC, improving the reconstruction of dark sector signals and proposing a comprehensive search strategy.

Contribution

It introduces a novel approach using ISR to identify semi-visible jets, including new observables and a complete search strategy for dark shower models.

Findings

ISR improves the identification and reconstruction of semi-visible jets.

New observables effectively measure the dark hadron fraction.

Proposed strategy covers the entire model parameter space.

Abstract

We investigate the potential to search for semi-visible jets (SVJs) at the Large Hadron Collider (LHC) using initial-state radiation (ISR). Both photon ISR and jet ISR channels are considered, using a benchmark signal model with the decay of a leptophobic $Z^\prime$ mediator forming two SVJs. We compare and extend several techniques to decompose the missing transverse momentum into per-jet contributions, in order to reconstruct the mediator mass and to define a new observable measuring the fraction of invisible dark hadrons. The presence of ISR facilitates the identification of the SVJs, and the resulting boost improves the resolution of the observables, especially for models with high invisible fractions. We combine the two observables to propose a complete search strategy and discuss an extension of the strategy to probe the whole model parameter space.