The $750$ GeV Diphoton Excesses in a Realistic D-brane Model
  We study the diphoton excesses near $750$ GeV recently reported by the ATLAS and CMS collaborations within the context of a phenomenologically interesting intersecting/magnetized D-brane model on a toroidal orientifold. It is shown that the model contains a SM singlet scalar as well as vector-like quarks and leptons. In addition, it is shown that the singlet scalar has Yukawa couplings with vector-like quarks and leptons such that it may be produced in proton-proton collisions via gluon fusion as well as decay to diphotons through loops involving the vector-like quarks. Moreover, the required vector-like quarks and leptons may appear in complete $SU(5)$ multiplets so that gauge coupling unification may be maintained. Finally, it is shown that the diphoton signal may be explained within the model. 
Tianjun Li, James A. Maxin, Van E. Mayes, Dimitri V. Nanopoulos
hep-ph hep-th