It has been widely known that bino-like dark matter in the supersymmetric (SUSY) theories in general suffers from over-production. The situation can be drastically improved if gluinos have a mass slightly heavier than the bino dark matter as they reduce the dark matter abundance through coannihilation. In this work, we consider such a bino-gluino coannihilation scenario in high-scale SUSY models, which can be actually realized when the squark-mass scale is less than 100-1000 TeV. We study the prospects for exploring this bino-gluino coannihilation scenario at the LHC. We show that the searches for long-lived colored particles with displaced vertices or large energy loss offer a strong tool to test this scenario in collider experiments.
arXiv:1504.00504v2 [hep-ph] 2 Jul 2015The first stage of the LHC running has pointed a possible direction for the actual realization of the supersymmetric (SUSY) Standard Model (SM). First and foremost, the observed SM-like Higgs boson [1] with a mass of about 125 GeV [2] implies that the mass scale of SUSY particles is higher than the electroweak scale; the radiative corrections by stops easily lift up the Higgs mass from the tree-level value predicted to be less than the Z-boson mass in the minimal SUSY SM [3], if the stop masses are far above the electroweak scale [4,5]. This is in fact consistent with lack of any evidence in the SUSY searches so far [6,7]. A relatively high SUSY breaking scale offers further advantages for SUSY SMs. For instance, heavy masses of SUSY particles suppress the flavor changing neutral current processes as well as the electric dipole moments of the SM particles [8,9], which are stringently constrained by the low-energy precision experiments. Moreover, such heavy SUSY particles reduce the proton decay rate via the color-triplet Higgs exchange [10] and make the simplest version of the SUSY grand unification model [11] viable. In cosmology, the gravitino problem is evaded when the gravitino mass is high enough [12]. These attractive points stimulate quite a few studies of high-scale SUSY models [13][14][15][16][17][18][19][20][21].An order parameter of SUSY breaking is the gravitino mass m 3/2 . If the SUSY breaking effects are transmitted to the visible sector via the gravitational interactions (or other interactions suppressed by some high-scale cutoff such as the Planck scale), then the soft SUSY-breaking scalar masses are induced with their size being O(m 3/2 ). In this case, the scalar SUSY particles typically have masses of the order of m 3/2 ; from now on, we express the typical masses of these scalar particles by m ∼ m 3/2 . The masses of the fermionic SUSY particles (gauginos and Higgsinos) are, on the other hand, dependent on models, since their mass terms can be suppressed if there exist additional symmetries. For example, the gaugino masses become much smaller than the gravitino mass if the SUSY breaking fields are charged under some symmetry. In this case, these masses are generated by quantum effects, such as anomaly mediation contribution...
