A feasibility study of the measurement of Higgs pair creation at a   Photon Linear Collider
  We studied the feasibility of the measurement of Higgs pair creation at a Photon Linear Collider (PLC). From the sensitivity to the anomalous self-coupling of the Higgs boson, the optimum $\gamma \gamma$ collision energy was found to be around 270 GeV for a Higgs mass of 120 GeV/$c^2$. We found that large backgrounds such as $\gamma \gamma \rightarrow W^+W^-, ZZ,$ and $b\bar{b}b\bar{b}$, can be suppressed if correct assignment of tracks to parent partons is achieved and Higgs pair events can be observed with a statistical significance of $\sim 5 \sigma$ by operating the PLC for 5 years. 
Shin-ichi Kawada, Nozomi Maeda, Tohru Takahashi, Katsumasa Ikematsu,   Keisuke Fujii, Yoshimasa Kurihara, Koji Tsumura, Dais...
hep-ph hep-ex