Low-Scale and Gauge-Mediated Supersymmetry Breaking at the Fermilab Tevatron Run II

TL;DR

The paper addresses the collider phenomenology of low-scale SUSY breaking at the Fermilab Tevatron Run II, focusing on gauge-mediated scenarios with a nearly massless Goldstino LSP. It systematically classifies signatures by NLSP identity and decay length, deriving decay rates and exploring whether decays are prompt, displaced, or occur outside the detector, with implications for event selection. It catalogs a wide range of signatures, from standard missing-energy channels to exotic topologies such as displaced photons, large negative impact parameter tracks, kink tracks, highly ionizing tracks, charge-exchange tracks, time-of-flight signals, and Higgs-tagged events. It presents Run II discovery and exclusion reach estimates under realistic backgrounds and argues that the distinctive Goldstino-driven signatures offer robust opportunities to observe Higgs bosons in SUSY events.

Abstract

The prospects for discovering and studying signals of low-scale supersymmetry breaking models at the Tevatron Run II and beyond are explored. These models include gauge-mediated supersymmetry breaking as the most compelling and concrete realization, but more generally are distinguished by the presence of a nearly massless Goldstino as the lightest supersymmetric particle. The next-lightest supersymmetric particle(s) (NLSP) decays to its partner and the Goldstino. Depending on the supersymmetry breaking scale, these decays can occur promptly or on a scale comparable to or larger than the size of a detector. A systematic analysis based on a classification in terms of the identity of the NLSP and its decay length is presented. The various scenarios are discussed in terms of signatures and possible event selection criteria. The Run II and beyond discovery and exclusion reaches, including the effects of background, are detailed for the most compelling cases. In addition to standard event selection criteria based on missing energy and photons, leptons, jets, taus, tagged b-jets, or reconstructed Z-bosons, more exotic signals of metastable NLSPs such as displaced photons, large negative impact parameter tracks, kink tracks, both opposite and same-sign highly ionizing tracks, time of flight measurements, charge-changing tracks, charge-exchange tracks, and same-sign di-top events are investigated. The interesting possibility of observing a Higgs boson signal in events that are efficiently "tagged" by the unique signatures of low-scale supersymmetry breaking is also considered.

Figures (2)

• Figure 1: The Goldstino ${\widetilde{G}}$ derivatively couples each particle $X$ to its superpartner $\widetilde{X}$, with an interaction strength inversely proportional to $F$.
• Figure 2: NLSP decay length, $c \tau(\widetilde{X} \rightarrow X \widetilde{G})$, in meters, as a function of the supersymmetry breaking scale, $\sqrt{F}$, in TeV. From top to bottom the lines are for an NLSP mass $m_{\tilde{X}}$ = 50, 100, 150, 200, 250 GeV and with $m_X=0$ and $\kappa =1$.