Dark gauge-mediated supersymmetry breaking with a massless dark photon

TL;DR

This paper explores a dark gauge-mediated supersymmetry breaking model with a massless dark photon, revealing unique superpartner spectra, potential collider signatures, and cosmological implications due to kinetic mixing and stable messenger particles.

Contribution

It introduces a novel dark GMSB framework with kinetic mixing effects, predicting distinctive superpartner spectra and experimental signatures not present in conventional models.

Findings

Significant superpartner spectrum distortions due to kinetic mixing.

Light Higgsino arising from altered electroweak symmetry breaking conditions.

Presence of a stable, fractionally charged messenger particle.

Abstract

We study dark gauge-mediated supersymmetry breaking (dark GMSB) in a theory with a new unbroken $U(1)_{D}$ local symmetry and massless dark photon. Messenger fields charged under both Standard Model and dark gauge symmetries produce new soft supersymmetry-breaking terms due to gauge kinetic mixing between $U(1)_Y$ hypercharge and $U(1)_D$. We show that large kinetic mixing induces significant distortions to the superpartner spectra relative to conventional GMSB. Notably, shifts in the Higgs soft masses impact the conditions for electroweak symmetry breaking, lowering the $\mu$ parameter and yielding a relatively light Higgsino that may be accessible at the LHC. Furthermore, for very simple messenger representations, a very light bino-dark photino mixed state is present in the spectrum, which may be probed through exotic Higgs boson decays at future Higgs factories. We also examine the cosmological and phenomenological consequences of the messengers, the lightest of which is absolutely stable and carries fractional electric charge.