Missing Energy Signatures of Dark Matter at the LHC

TL;DR

This paper analyzes LHC mono-jet and mono-photon searches to set limits on dark matter interactions with Standard Model particles, finding that high p_T cuts improve sensitivity and that LHC constraints can surpass direct detection for certain operators.

Contribution

It provides a comprehensive comparison of mono-jet and mono-photon search sensitivities, translating collider limits into bounds on dark matter cross sections and exploring the validity of effective field theory approaches.

Findings

High p_T cuts increase sensitivity to dark matter at the LHC.

LHC mono-jet searches can outperform direct detection for certain operators up to 1 TeV.

Constraints exclude thermal relic annihilation for dark matter below 15-70 GeV depending on operator.

Abstract

We use ATLAS and CMS searches in the mono-jet + missing energy and mono-photon + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing mono-jet analyses and find that searches with high p_T cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter-Standard Model interactions, and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular spin-independent dark matter-gluon couplings and spin-dependent dark matter-quark couplings, LHC constraints from the mono-jet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below ~ 15-70 GeV, depending on the Lorentz structure of the effective couplings. Mono-photon limits are somewhat weaker than mono-jet bounds, but still provide an important cross check in the case of a discovery in mono-jets. We also discuss the possibility that dark matter--Standard Model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. We also discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.