Higgs pair production at a linear e+e- collider in models with large   extra dimensions
  In this paper, we will derive the cross section formula for the Higgs pair production at a linear $e^+e^-$ collider in models with large extra dimensions and study the feasibility of its measurement through realistic Monte Carlo simulations. Since the process has essentially no Standard Model background, once produced, it will provide us with a very clean signature of physics beyond the Standard Model. Moreover, since the final state particles are spinless, the spin 2 of the intermediate virtual KK gravitons has to be conserved by the orbital angular momentum of the Higgs pair. This results in a very characteristic angular distribution of the final states. Taking into account finite detector acceptance and resolutions as well as initial state radiation and beamstrahlung, we demonstrate in this paper that, given a sufficiently high center of mass energy, the angular distribution of the Higgs pair is indeed measurable at the linear collider and will allow us to prove the spin 2 nature of the KK gravitons exchanged in the s-channel. 
Nicolas Delerue, Keisuke Fujii and Nobuchika Okada