Probing axino LSP from diphoton events with large missing transverse energy

In a supersymmetry model with an axino as the lightest supersymmetric particle (LSP) and a Bino as the next LSP (NLSP), supersymmetric particle production ends up with including two Binos, followed by each Binoʼs decaying into a photon and an axino. Final states are diphoton with large missing energy. In a benchmark scenario, we have comprehensively studied the implication of γγ+E̸(T) data from the ALEPH, CDF II, ATLAS and CMS experiments. No excess over the standard model backgrounds can be explained in this model if the Bino NLSP decays outside the detector. Long life time of the Bino is possible because of high Peccei-Quinn symmetry breaking scale fa. The ALEPH and CDF II data put a very strong bound on fa for light Bino case with mB˜≲150GeV: the narrow hadronic axion window around fa∼106GeV is completely closed. The recent ATLAS and CMS data show very interesting bound on fa≳105GeV for the Bino mass below 700 GeV. This is already stronger than the previous laboratory bounds.