Likelihood Analysis of the Sub-GUT MSSM in Light of LHC 13-TeV Data

We describe a likelihood analysis using MasterCode of variants of the MSSM in which the soft supersymmetry-breaking parameters are assumed to have universal values at some scale $M_\mathrm{in}$ below the supersymmetric grand unification scale $M_\mathrm{GUT}$ , as can occur in mirage mediation and other models. In addition to $M_\mathrm{in}$ , such ‘sub-GUT’ models have the 4 parameters of the CMSSM, namely a common gaugino mass $m_{1/2}$ , a common soft supersymmetry-breaking scalar mass $m_0$ , a common trilinear mixing parameter A and the ratio of MSSM Higgs vevs $\tan \beta $ , assuming that the Higgs mixing parameter $\mu > 0$ . We take into account constraints on strongly- and electroweakly-interacting sparticles from $\sim 36$ /fb of LHC data at 13 TeV and the LUX and 2017 PICO, XENON1T and PandaX-II searches for dark matter scattering, in addition to the previous LHC and dark matter constraints as well as full sets of flavour and electroweak constraints. We find a preference for $M_\mathrm{in}\sim 10^5$ to $10^9 \,\, \mathrm {GeV}$ , with $M_\mathrm{in}\sim M_\mathrm{GUT}$ disfavoured by $\Delta \chi ^2 \sim 3$ due to the $\mathrm{BR}(B_{s, d} \rightarrow \mu ^+\mu ^-)$ constraint. The lower limits on strongly-interacting sparticles are largely determined by LHC searches, and similar to those in the CMSSM. We find a preference for the LSP to be a Bino or Higgsino with $m_{\tilde{\chi }^0_{1}} \sim 1 \,\, \mathrm {TeV}$ , with annihilation via heavy Higgs bosons H / A and stop coannihilation, or chargino coannihilation, bringing the cold dark matter density into the cosmological range. We find that spin-independent dark matter scattering is likely to be within reach of the planned LUX-Zeplin and XENONnT experiments. We probe the impact of the $(g-2)_\mu $ constraint, finding similar results whether or not it is included.