Xenon100 collaboration gives a stringent constraint on spin-independent elastic WIMP-nucleon scattering cross section. Ton-scale detectors for direct detection experiments are expected to yield significantly improved sensitivities. Direct Detection of Dark Matter Degenerate with Colored Particle in Mass Natsumi Nagata (Nagoya University, The University of Tokyo) Direct Detection of Dark Matter Degenerate with Colored Particle in Mass Natsumi Nagata (Nagoya University, The University of Tokyo) J. Hisano, K. Ishiwata, and N. Nagata, arXiv: KMI Inauguration Conference (October 24-26, 2011) (for WIMPs of mass 50 GeV) IceCubeIceCube Model/AssumptionModel/Assumption Effective interaction of wino DM with light quarks and gluon Twist-2 operator ー： Spin-dependent ー： Spin-independent ResultsResults ConclusionConclusion AbstractAbstract We explore the direct detection of the dark matter in the universe, assuming the dark matter particles are degenerate in mass with new colored particles below TeV scale. The scenario with such a mass spectrum is difficult to be confirmed or excluded by the present analysis at the LHC experiments because the QCD jets in the cascade decay of the new particles produced in the proton-proton collision are too soft to be triggered in the event selection. It is shown that both of the spin- independent and spin-dependent couplings of the dark matter with a nucleon are enhanced and the scattering cross section may reach even the current bound of the direct detection experiments. Then such a degenerate scenario may be tested in the direct detection experiments. IntroductionIntroduction Existence of Dark Matter (DM) A variety of observational evidences indicate the existence of non-baryonic dark matter. One of the most attractive candidates is Weakly Interacting Massive Particles (WIMPs) DM Direct Detection Experiments WIMP DM search at the LHC DM LHC Hard Jets + Large Missing Transverse Energy The LHC experiments have already presented severe constraints on various DM models. However, these constraints are not directly applied if the colored particles in the new physics are nearly degenerate with the WIMPs in mass. Degenerate scenario In the case where the mass difference between DM and colored particles is about 100 GeV Jets are too soft to be triggered and the missing energy signature would not be observed at the LHC. (We consider such scenario) [XENON100 collaboration, arXiv: ] We explore possibilities for probing the degenerate scenario in terms of the direct detection experiments. [IceCube collaboration, arXiv: ] A search for muon neutrinos from DM annihilations in the Sun. This experiment offers excellent sensitivities to the spin-dependent WINP-nucleon scattering cross section. (with WIMP mass, 100 GeV-1 TeV) We also consider this experiment in order to look into the degenerate scenario. In the following discussion, we consider a simple case Pure wino DM in the MSSM  DM is pure wino  The first generation squarks are degenerate with wino DM in mass  The other squarks are heavy enough to evade current bound  Gluino is either degenerate with wino in mass or much heavier than the present limit Let us write down the effective interactions of wino DM with light quarks and gluon. The coefficients of these effective operators are to be determined in the subsequent calculation. Pure wino DM interacts with quarks via the squark exchange interaction at tree- level. The mass degeneracy between DM and the first generation squarks is parameterized as Tree-level diagram The effective couplings are enhanced when the squark masses are degenerate with the DM mass.  The scattering cross section of DM with nucleon is considerably enhanced when the mass difference between DM and colored particles is less than about 100 GeV with the DM mass below 1 TeV.  The current and future direct detection experiments might shed light on the nature of DM and new colored particles when their masses are degenerate.  We have also evaluated pure bino and higgsino DM cases. We found that the resultant cross sections are in general smaller than that for wino DM.  The extension to more general neutralino DM is to be discussed.  Similar calculation for the Kaluza-Klein DM in the minimal Universal Extra Dimension model is carried out in [arXiv: , ]. The enhancement of the cross sections is also observed in that case. The spin-dependent scattering cross sectionThe spin-independent scattering cross section ΔM= 50 GeV 100 GeV 150 GeV 200 GeV (From top to bottom) ΔM= 50 GeV 100 GeV 150 GeV 200 GeV (From top to bottom) IceCube IceCube(sens.) The DM-nucleon scattering cross section is generally enhanced in the degenerate scenario. DM searches might be complementary to the LHC experiments.  In our calculation, we also include the wino-quark interaction at one-loop level via the weak interaction which becomes sizable when the DM mass is larger than 1 TeV (See [arXiv: , ]).  Gluon contribution is not negligible at all. The precise evaluation of the gluon contribution is carried out in [arXiv: , , ].