Possible Effects of a Hidden Valley on Supersymmetric Phenomenology

TL;DR

The paper investigates hidden-valley models in which a v-sector with its own gauge dynamics and a mass gap interacts with the Standard Model through portals such as a $Z'$ and Higgs mixing. When the LSP resides in the v-sector, conventional SUSY missing-energy signals can be dramatically diluted, and LSsP decays generate multiple v-hadrons that decay to soft visible states or yield displaced vertices, altering collider signatures. It analyzes v-hadron spectra, LSsP decay rates, and final-state topologies across 2LF and 1LF regimes, outlining how these signals could manifest at Tevatron- and LHC-era experiments and proposing detection strategies, including highly displaced vertices and timing-based approaches. The work also discusses broader applicability to extra-dimensional and parity-based models, emphasizes the role of LHCb in such searches, and calls for revised limits and dedicated simulations to ensure these phenomena are not overlooked in collider programs.

Abstract

A hidden valley sector may havea profound impact on the classic phenomenology of supersymmetry. This occurs if the LSP lies in the valley sector. In addition to reducing the standard missing energy signals and possibly providing displaced vertices (phenomena familiar from gauge-mediated and R-parity-violating models) it may lead to a variable multiplicity of new neutral particles, whose decays produce soft jets and/or leptons, and perhaps additional displaced vertices. Combined, these issues might obscure supersymmetric particle production from search strategies used on current Tevatron data and planned for the LHC. The same concerns arise more generally for any model that has a symmetry (such as T-parity or KK-parity) realized nontrivially in both the standard-model and the hidden-valley sectors. Possible strategies for experimental detection are discussed, and the potential importance of the LHCb detector is noted.

Figures (6)

• Figure 1: Schematic view of production and decay of v-hadrons. While LEP was unable to penetrate the barrier separating the sectors, LHC may easily produce v-particles. These form v-hadrons, some of which decay to standard model particles.
• Figure 2: Schematic view of production and decay of SM superpartners. Each superpartner decays to hard jets/leptons and an LSsP; the LSsP then decays to an LSvP plus other v-hadrons, some of which decay to softer jet/lepton pairs.
• Figure 3: The production and subsequent decay of a chargino and neutralino, showing the two LSsPs decaying to various v-hadrons, some of which decay visibly. Invisible R-parity-even (-odd) v-hadrons, are shown as solid (dashed) lines; in particular, an LSvP, labelled $\tilde{R}$, is produced in each of the LSsP decays.
• Figure 4: Partial spectrum and decay modes in the two-light-flavor regime (left) and one-light-flavor regime (right); the latter is partly guesswork.
• Figure 5: Various possible decays of an LSsP to an LSvP. (a) At one extreme, prompt neutralino decays to a v-quark and v-squark via mixing of the neutralino with the $\tilde{Z}'$ or $\tilde{\phi}$. (b) Slow decay of a neutralino to a v-gluon and v-gluino via a v-quark/v-squark loop. (c) Slow decay of a gluino to $q\bar{q}$ plus a v-quark and v-squark. (d) Very slow decay of a gluino to a v-gluino.