Feasibility study of measurement of Higgs pair creation in a gamma gamma   collider
  We studied the feasibility of measurement of Higgs pair creation in a gamma gamma collider. We found the optimum collision energy is around 270 GeV from the sensitivity study with Higgs boson mass of 120 GeV/c^2. Main backgrounds are gamma gamma to WW, gamma gamma to ZZ, and gamma gamma to bbbb at the optimum collision energy. The preliminary analysis shows HH could be observed with the statistical significance of about 5 sigma when we chose correct assignment of a track by using color singlet information. 
Shin-ichi Kawada, Katsumasa Ikematsu, Tohru Takahashi, Keisuke Fujii,   Yoshimasa Kurihara
hep-ex