An operator basis for the Standard Model with an added scalar singlet
  Motivated by the possible di-gamma resonance at 750 GeV, we present a basis of effective operators for the Standard Model plus a scalar singlet at dimensions 5, 6, and 7. We point out that an earlier list at dimensions 5 and 6 contains two redundant operators at dimension 5. 
Ben Gripaios and Dave Sutherland
hep-ph hep-ex