Reach of the high-energy LHC for gluinos and top squarks in SUSY models with light Higgsinos

摘要

We examine the top squark (stop) and gluino reach of the proposed 33 TeVenergy upgrade of the LargeHadron Collider (LHC33) in the Minimal Supersymmetric Standard Model (MSSM) with light Higgsinosand relatively heavy electroweak gauginos. In our analysis, we assume that stops decay to Higgsinos viat_1 → t Z_1, t_1 → tZ_2, and t_1 → bW_1 with branching fractions in the ratio 1∶1∶2 (expected if the decayoccurs dominantly via the superpotential Yukawa coupling), while gluinos decay via g → t t_1 or via threebodydecays to third-generation quarks plus Higgsinos. These decay patterns are motivated by models ofnatural supersymmetry where Higgsinos are expected to be close in mass to m_Z, but gluinos may be asheavy as 5–6 TeV, and stops may have masses up to ～3 TeV. We devise cuts to optimize the signals fromstop and gluino pair production at LHC33. We find that experiments at LHC33 should be able to discoverstops with >5σ significance if m_(t1)< 2.3 (2.8) [3.2] TeV for an integrated luminosity of 0.3 (1) [3] ab~(−1).The corresponding reach for gluinos extends to 5 (5.5) [6] TeV. These results imply that experiments atLHC33 should be able to discover at least one of the stop or gluino pair signals even with an integratedluminosity of 0.3 ab~(−1) for natural supersymmetry models with no worse than 3% electroweak fine-tuningand quite likely both gluinos and stops for an integrated luminosity of 3 ab~(−1).