Search for Dark Matter direct production in the monophoton plus missing transverse momentum final state in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

This paper presents a search for dark matter pair production in asso- ciation with an energetic photon in 20 . 3fb − 1 of pp collisions collected at √ s =8TeV by the ATLAS detector at the LHC. The final state investigated in this analysis is defined by large missing transverse momentum ( E miss T > 150 GeV) and by the pres- ence of an energetic photon ( p T > 125 GeV). Observations in data are compared to the Standard Model expectations and no significant excess is found. A model- independent limit is set on the presence of new physics in data. Data are also interpreted in the framework of effective field theories which describe the interaction between dark matter and incoming partons as a contact interaction parameterized by a set of dimensional operators.