Goldstini

TL;DR

This work broadens SUSY phenomenology by allowing multiple sequestered SUSY-breaking sectors, producing several goldstini in addition to the gravitino. A central result is that all uneaten goldstini acquire a universal tree-level mass \(m_a = 2 m_{3/2}\) from supergravity, while their couplings to the SSM can be significantly stronger than the gravitino’s, depending on the SUSY-breaking scales \(F_i\) and mediation details. The paper develops the theoretical framework (Stückelberg and conformal compensator viewpoints), analyzes deviations from the fully sequestered limit, and explores distinctive collider signatures such as gravitino-like states with wrong mass-interaction relations, gravitinoless gauge mediation, difermion final states with fixed ratios, and displaced-vertex monojets, along with cosmological implications including stability, BBN constraints, and possible goldstini dark matter. These results imply new avenues for discovering or constraining multiple-sector SUSY breaking through collider experiments and cosmological observations, potentially allowing direct measurements of the two goldstini states. The findings significantly expand the phenomenological landscape beyond conventional single-sector SUSY breaking, offering robust predictions that can be tested at current and future experiments.

Abstract

Supersymmetric phenomenology has been largely bound to the hypothesis that supersymmetry breaking originates from a single source. In this paper, we relax this underlying assumption and consider a multiplicity of sectors which independently break supersymmetry, thus yielding a corresponding multiplicity of goldstini. While one linear combination of goldstini is eaten via the super-Higgs mechanism, the orthogonal combinations remain in the spectrum as physical degrees of freedom. Interestingly, supergravity effects induce a universal tree-level mass for the goldstini which is exactly twice the gravitino mass. Since visible sector fields can couple dominantly to the goldstini rather than the gravitino, this framework allows for substantial departures from conventional supersymmetric phenomenology. In fact, this even occurs when a conventional mediation scheme is augmented by additional supersymmetry breaking sectors which are fully sequestered. We discuss a number of striking collider signatures, including various novel decay modes for the lightest observable-sector supersymmetric particle, gravitinoless gauge-mediated spectra, and events with multiple displaced vertices. We also describe goldstini cosmology and the possibility of goldstini dark matter.

Figures (7)

• Figure 1: A schematic depiction of a scenario in which the SSM sector couples to only one of the SUSY breaking sectors. Note that this setup still leads to interactions between SSM fields and goldstini in the sequestered sectors, since the goldstino of the sector coupling to the SSM is in general a linear combination of the gravitino and uneaten goldstini.
• Figure 2: A schematic depiction of a scenario in which sectors 1 and 2 have direct interactions to the SSM sector via operators suppressed by $\Lambda_1$ and $\Lambda_2$, respectively (double lines). These interactions induce direct couplings between sectors 1 and 2 through radiative corrections (dashed line).
• Figure 3: Feynman diagrams which induce direct couplings between sectors 1 and 2. There is always at least one factor of $1/16\pi^2$ coming from a loop of SSM fields. Depending on the details of the underlying theory, there may be additional loop factors, for instance if the $\int\! d^2\theta\, X_{1} {\cal W}^\alpha {\cal W}_\alpha/\Lambda_1$ coupling itself is generated at one loop.
• Figure 4: A contour plot of $R$ in Eq. (\ref{['eq:Rcoeff']}) as a function of $\tilde{m}_1^2/\tilde{m}_2^2$ and $F_1/F_2$. When $|\tilde{m}_1^2| \mathrel{\hbox{$<$$\sim$}} |\tilde{m}_2^2|$, $R$ is greater than unity for a wide range of $F_1/F_2$, so that the SSM sector fields couple more strongly to the uneaten goldstino than to the gravitino.
• Figure 5: If $F_1 \approx F_2$ and $\tilde{m}_1 \approx \tilde{m}_2$, then the SSM states couple to $\zeta$ and $\tilde{G}$ with similar strengths. In particular, if $\zeta$ and $\tilde{G}$ are lighter than all the SSM superpartners, then the LOSP decays into $\zeta$ or $\tilde{G}$ with non-negligible branching ratios. This allows for the possibility of measuring the masses of both $\zeta$ and $\tilde{G}$, providing smoking gun evidence for multiple sector SUSY breaking.