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This paper reinterprets fourteen years of ATLAS data to test versions of supersymmetry (SUSY) where a symmetry called R-parity can be broken with variable strength. R-parity is a rule that, if respected, makes the lightest supersymmetric particle (the LSP) stable and invisible in the detector. If R-parity is broken, the LSP can decay to ordinary particles. How fast it decays depends on the size of the R-parity-violating (RPV) coupling. The authors use the full ATLAS Run 2 dataset of proton–proton collisions at 13 TeV, corresponding to 140 inverse femtobarns, and they reinterpret thirteen existing SUSY searches to cover the full range from prompt LSP decays to long-lived LSPs that decay away from the collision point.
The team considered six simplified RPV SUSY models. Simplified models keep only the particles and decays needed to set limits, so they are easier to test. Typical particles studied include gluinos (the partner of the gluon), top squarks (partners of top quarks), tau-sleptons (partners of tau leptons), higgsinos (partners of the Higgs boson), charginos and neutralinos (mixed partners of electroweak and Higgs bosons). The reinterpretation used the RECAST framework for some cases and the original analysis code for others. Importantly, the authors ran a full detector simulation with Geant4 so they could model displaced decays and other long-lived particle signatures accurately. They also evaluated experimental uncertainties as a function of how far the LSP decay vertex is displaced from the collision point.
The paper sets new 95% confidence-level limits on sparticle masses across different RPV coupling strengths and LSP lifetimes. For a model with pair-produced gluinos that decay to final states rich in top quarks, gluinos lighter than 1.8 TeV are excluded for all values of the RPV coupling. In gluino models that decay to first- and second-generation quarks, excluded gluino masses range from about 1.6 to 2.2 TeV (or 1.6 to 2.5 TeV) depending on the choice of RPV coupling type. Top-squark masses are excluded up to 2.4 TeV when a baryon-number-violating coupling (called λ′′) is large, while the exclusion falls to roughly 1.0–1.7 TeV for lower or intermediate λ′′ values. Tau-slepton masses between 180 and 340 GeV are excluded when certain lepton-number-violating couplings (λ) are smaller than 10^−4. Higgsino masses are excluded up to about 800 GeV–1.0 TeV when a particular coupling labeled λ_i33 exceeds 4×10^−5. These results extend sensitivity to a wider range of long-lived particle behaviours than previous studies.
Why this matters: many existing SUSY searches assume either exact R-parity (stable LSP) or very large RPV couplings (prompt LSP decays). Between those extremes lies an intermediate regime where the LSP lives long enough to decay at a displaced point inside the detector. That intermediate regime has been less constrained. By reusing and adapting a broad set of ATLAS searches and by simulating displaced decays carefully, the study fills in those gaps. It shows that searches designed for one type of SUSY can still have meaningful sensitivity to other scenarios when reinterpreted properly.
Important caveats and limitations: the study uses simplified models in which typically only one RPV coupling is non-zero. Realistic models might have several non-zero couplings at once, which could change decay patterns and lifetimes. The LSP lifetime depends not only on the RPV coupling but also on the masses of the intermediate sleptons or squarks; those masses were set or chosen to keep the study tractable, and the limits therefore depend on those choices. The reinterpretation also reuses many elements of the original analyses—object definitions, background estimates and statistical models—which is efficient but means the limits inherit the assumptions and limitations of those analyses. Finally, the results apply to the specific models and parameter choices tested; they do not rule out all possible RPV scenarios.