Current Large Hadron Collider (LHC) analyses are blind to compressed supersymmetry (SUSY) models with sleptons near the lightest super partner (LSP) in mass: ml − mχ0 1 ≡ ∆m 60 GeV. We present a search sensitive to the very compressed range 3 GeV < ∆m < 24 GeV using the channel pp →l +l− + jet → l + l −χ0 1χ 0 1 + jet with soft same-flavor leptons and one hard jet from initial state radiation (p j T > 100 GeV). The sleptons recoil against the jet boosting them and their decay products, making the leptons detectable and providing substantial missing transverse momentum. We use the kinematic variable m T2 along with a different-flavor control region to reduce the large standard model backgrounds and control systematic uncertainty. We find the analysis should allow LHC14 with 100 fb −1 to search for degenerate left-handed selectrons and smuons in the compressed region up to ml L 150 GeV. In addition, it should be sensitive to ml L 110 GeV for the very challenging case of auto-concealed SUSY, in which left-handed sleptons decay to the Kaluza-Klein tower of a modulino LSP which lives in d = 6 extra dimensions. In both the compressed spectrum and auto-concealed SUSY scenarios this analysis will need more data to improve on LEP2 limits for right-handed sleptons due to their smaller cross sections.

In supersymmetric (SUSY) theories with extra dimensions the visible energy in sparticle decays can be significantly reduced and its energy distribution broadened, thus significantly weakening the present collider limits on SUSY. The mechanism applies when the lightest supersymmetric particle (LSP) is a bulk state -e.g. a bulk modulino, axino, or gravitino -the size of the extra dimensions 10 −14 cm, and for a broad variety of visible sparticle spectra. In such cases the lightest ordinary supersymmetric particle (LOSP), necessarily a brane-localised state, decays to the Kaluza-Klein (KK) discretuum of the LSP. This dynamically realises the compression mechanism for hiding SUSY as decays into the more numerous heavier KK LSP states are favored. We find LHC limits on right-handed slepton LOSPs evaporate, while LHC limits on stop LOSPs weaken to ∼ 350 ÷ 410 GeV compared to ∼ 700 GeV for a stop decaying to a massless LSP. Similarly, for the searches we consider, present limits on direct production of degenerate first and second generation squarks drop to ∼ 450 GeV compared to ∼ 800 GeV for a squark decaying to a massless LSP. Auto-concealment typically works for a fundamental gravitational scale of M * ∼ 10 ÷ 100 TeV, a scale sufficiently high that traditional searches for signatures of extra dimensions are mostly avoided. If superpartners are discovered, their prompt, displaced, or stopped decays can also provide new search opportunities for extra dimensions with the potential to reach M * ∼ 10 9 GeV. This mechanism applies more generally than just SUSY theories, pertaining to any theory where there is a discrete quantum number shared by both brane and bulk sectors.