Associated production of a photon with dark matter pair at the ILC   within the Littlest Higgs model with T-parity
  Within the context of the Littlest Higgs model with T-parity, the heavy photon ($A_{H}$) is supposed to be an ideal dark matter (DM) candidate. One direct proof of validity of the model is to produce the heavy photon at collider. In this paper, we investigate the associated production of a photon with heavy photon pair at the planned international $e^ +e^ -$ linear collider (ILC), i.e., $ e^+ e^-\to A_{H}A_{H}{\gamma}$ and show the distributions of the transverse momenta of the photon. The numerical results indicate that the heavy photon production rate could reach several $fb$ at the low mass parameter space and the characteristic signal is a single high energetic photon and missing energy, carried by the heavy photons. All in all, it can be good chance to observe the heavy photon via this process with the high yearly luminosity of the ILC. 
Qing-Peng Qiao, Bin Xu
hep-ph