F-theory and the LHC: Stau Search

TL;DR

This work analyzes minimal F-theory GUTs in which the gravitino is the LSP with $m_{3/2}\sim 10-100$ MeV and the NLSP is typically a quasi-stable stau, producing striking heavy charged tracks at the LHC. By scanning parameter ranges in $N_{10}=1,2$, $\Lambda$, and PQ deformation $\Delta_{PQ}$, and fixing a messenger scale $M_{mess}\sim 10^{12}$ GeV, the authors map NLSP identities and decay topologies, and simulate collider signatures with PYTHIA using spectrum information from SOFTSUSY/Decay/BRIDGE. They develop inclusive and exclusive search channels to probe stau production, estimate discovery reach at 7–14 TeV, and discuss the potential to stop and study decays of staus to measure the SUSY-breaking scale $\sqrt{F}$, as well as prospects for mass reconstruction. Finally, they compare F-theory GUTs to minimal gauge mediation look-alikes, showing that high-precision sparticle masses—especially sleptons—can distinguish these scenarios and provide insight into the underlying PQ structure and UV completion. The results have direct implications for LHC searches of long-lived charged particles and for testing string-inspired SUSY-breaking schemes.

Abstract

F-theory GUT models favor a relatively narrow range of soft supersymmetry breaking parameters in the MSSM Lagrangian. This leads to the specific predictions that a 10-100 MeV mass gravitino is the LSP, and the NLSP is quasi-stable, with a lifetime between a second to an hour. In a wide range of parameter space, the NLSP turns out to be a stau, though a bino-like lightest neutralino is also possible. Focusing on F-theory GUTs with a stau NLSP, we study the discovery potential at the LHC for such scenarios. Models with a quasi-stable stau predict a striking signature of a heavy charged particle passing through the detector. As a function of the parameters of minimal F-theory GUTs, we study how many of such events to expect, and additional signatures correlated with the presence of quasi-stable staus. We also study the prospects for staus to become stopped in or near the detector, as well as potential ways to distinguish such models from minimal gauge mediation models with similar spectra.

Figures (29)

• Figure 1: Spectrum of an F-theory GUT Majorana neutrino scenario with $N_{10}=1$, $\Lambda=50$ TeV for minimal (red left columns) and maximal (blue right columns) PQ deformation of order $200$ GeV. At small values of the PQ deformation, the bino is the NLSP, whereas for larger values this transitions to the stau. Further note that at larger PQ deformation, the right-handed selectron and smuon are also lighter than the bino, and all of the sleptons are lighter than the second neutralino and lightest chargino.
• Figure 2: Contour plot indicating the relative masses of the bino, lightest stau and right-handed selectron as function of $\Delta_{PQ}$ and $M_{mess}$ in the representative F-theory GUT scenario with $N_{10} = 1$ and $\Lambda = 50$ TeV. There are three qualitatively different regions separated by the two lines where the bino is equal in mass to either the stau (upper line) or slectron (lower line). Here we also indicate the bino NLSP (upper left orange region) and stau NLSP (lower right cyan region) regimes of parameter space.
• Figure 3: Plot of the four lightest sparticle masses as a function of messenger scale $M_{mess}$. Here $N_{10}=1$, $\Lambda=50$ TeV, and we have displayed the values for zero PQ deformation (upper lines) and $\Delta _{PQ}=150$ GeV (lower lines). Note that the bino mass remains constant, both as a function of messenger scale and of PQ deformation.
• Figure 4: As a function of $\Delta_{PQ}$ and $\Lambda$, the masses of the sleptons will change relative to the gauginos. For F-theory GUTs with $N_{10}=1$ messengers, as $\Delta_{PQ}$ increases, there are three qualitative crossing regions where the stau becomes lighter than the bino, all sleptons become lighter than the second neutralino and lightest chargino, and the right-handed selectron and smuon become lighter than the bino. In the plot, the orange region to the left denotes the range of parameter space where the bino is the NLSP, and the cyan region to the right indicates the region of the stau NLSP.
• Figure 5: Mass spectrum of the sleptons and lightest chargino and two lightest neutralinos with $N_{10}=1$, $\Lambda=50$ TeV as a function of $\Delta_{PQ}$. At values of $\Delta_{PQ}\sim90$ GeV, the stau becomes the NLSP. At somewhat larger values of the PQ deformation, the sneutrinos become lighter than $\widetilde{\chi}_{2}^{0}$ and at larger values, the right-handed selectron and smuon become lighter than the bino. The dashed grey line at $100$ GeV denotes the present experimental bound on the mass of a quasi-stable stau.