Light Dark Matter Showering under Broken Dark $U(1)$ -- Revisited

TL;DR

This paper refines the modeling of dark matter showers in broken dark U(1) theories, demonstrating how shower patterns can reveal the dark matter fermion's chirality and the dark sector's mass origin.

Contribution

It derives comprehensive collinear splitting functions including helicity and dark Higgs effects, improving dark shower simulations and analysis methods.

Findings

Dark shower patterns can distinguish DM fermion chirality.

Dark jet energy profiles are nearly independent of DM energy.

Enhanced modeling reveals new features in dark matter shower signatures.

Abstract

It was proposed recently that different chiralities of the dark matter (DM) fermion under a broken dark U(1) gauge group can lead to distinguishable signatures at the LHC through shower patterns, which may reveal the mass origin of the dark sector. We study this subject further by examining the dark shower of two simplified models, the dubbed Chiral Model and the Vector Model. We derive a more complete set of collinear splitting functions with power corrections, specifying the helicities of the initial DM fermion and including the contribution from an extra degree of freedom, the dark Higgs boson. The dark shower is then implemented with these splitting functions, and the new features resulting from its correct modelling are emphasized. It is shown that the DM fermion chirality can be differentiated by measuring dark shower patterns, especially the DM jet energy profile, which is almost independent of the DM energy.