1. Direct Search and LHC Detection of the Simplest Dark Matter Model
Xiao-Gang He
NTU&SJTU
The Simplest Dark Matter Model
Direct Search
Implications for Higgs search at LHC
Discussions and Conclusions

2. 1. The Simplest Dark Matter Model
The simplest dark model is the darkon model: SM + real singlet D. Renormalizable interaction only with SM Higgs H With a Z2 symmetry, D -> - D. If not broken, D can play the role of stable dark matter.

3. D is stable, but can annihilate through h exchange

4. Relic density is given by

5. 2. Direct Search

7. 3. Implications for Higgs Search at LHC If Higgs mass is larger than 2 darkon mass, h can decay into darkon h -> DD, increasing invisible width.

8. 4. Discussions and Conclusions
If darkon has mass smaller than (m_B-m_K)/2, then B ->K DD possible t -> c DD too small a branching ratio (< 10^{-13}) for detection.

9. The simplest model for dark matter is the darkon model: SM + a real singlet D
It can provide the relic density in a large parameter space.
Direct search rule out some portion of parameter space, but still a large room left for future studies.
If darkon has a mass less than 2 time of Higgs mass, h -> DD increases the invisible width, affecting the way to detect Higgs boson at the LHC.
If darkon has a mass less than (m_B-m_K)/2, B -> K DD can occur.

10. Effects of 4th generation
If D heavier than 4th generation fermions, new channel open for annihilation. Modify relic density. New heavy quark change h -> gg, Modify rare decays B -> K DD, (factor of a few) t -> c D D, increase to 10^{-8} New t’(b’) -> t (b) DD

11. Relic density with 3 and 4 generations

12. Direct search with 3 and 4 generations

13. Invisible h -> DD with 3 and 4 generations