Iso-spin violating dark matter at the LHC

We consider a toy model of a dark matter where a standard model gauge singlet Dirac fermion couples to quarks through contact interactions, and the couplings to right-handed up and down quarks are different. We discuss how the effects of iso-spin violation in these couplings can be observed at the LHC. By studying events with large missing transverse momentum ( E/ T ), we show that the ratio of the mono-photon and mono-jet events is sensitive to the difference in the magnitudes of the couplings to up and down quarks, whereas dedicated study of di-jet plus E/ T events can reveal their relative sign.