Light Stops from Seiberg Duality
Csaba Csaki, Lisa Randall, John Terning
TL;DR
The paper addresses natural electroweak symmetry breaking in supersymmetry by embedding composite sectors through Seiberg duality at the edge of the conformal window, producing light composite states (Higgs, t, and electroweak gauginos) while keeping other MSSM fields heavy. This yields a NMSSM-like low-energy theory with a dynamical origin for the Higgs quartic and a 125 GeV Higgs without fine-tuning, and it predicts a hierarchical soft-breaking pattern where composites are protected from large SUSY-breaking. The authors analyze soft terms, present a concrete MCSSM construction, and explore four benchmark spectra, including stealth stop scenarios, highlighting distinctive collider phenomenology and reduced missing-energy signatures. The framework offers a testable, four-dimensional realization of stealth-like SUSY with natural EWSB and provides guidance for LHC searches targeting light composite stops and related states.
Abstract
If low-energy supersymmetry is realized in nature, a seemingly contrived hierarchy in the squark mass spectrum appears to be required. We show that composite supersymmetric theories at the bottom of the conformal window can automatically yield the spectrum that is suggested by experimental data and naturalness. With a non-tuned choice of parameters, the only superpartners below one TeV will be the partners of the Higgs, the electroweak gauge bosons, the left-handed top and bottom, and the right-handed top, which are precisely the particles needed to make weak scale supersymmetry breaking natural. In the model considered here, these correspond to composite (or partially composite) degrees of freedom via Seiberg duality, while the other MSSM fields, with their heavier superpartners, are elementary. The key observation is that at or near the edge of the conformal window, soft supersymmetry breaking scalar and gaugino masses are transmitted only to fundamental particles at leading order. With the potential that arises from the duality, a Higgs with a 125 GeV mass, with nearly SM production rates, is naturally accommodated without tuning. The lightest ordinary superpartner is either the lightest stop or the lightest neutralino. If it is the stop, it is natural for it to be almost degenerate with the top, in which case it decays to top by emitting a very soft gravitino, making it quite difficult to find this mode at the LHC and more challenging to find SUSY in general, yielding a simple realization of the stealth supersymmetry idea. We analyze four benchmark spectra in detail.