Majorana dark matter with a coloured mediator: collider vs direct and indirect searches

Abstract

We investigate the signatures at the Large Hadron Collider of a minimal model where the dark matter particle is a Majorana fermion that couples to the Standard Model via one or several coloured mediators. We emphasize the importance of the production channel of coloured scalars through the exchange of a dark matter particle in the t-channel, and perform a dedicated analysis of searches for jets and missing energy for this model. We find that the collider constraints are highly competitive compared to direct detection, and can even be considerably stronger over a wide range of parameters. We also discuss the complementarity with searches for spectral features at gamma-ray telescopes and comment on the possibility of several coloured mediators, which is further constrained by flavour observables.

The waning of the WIMP? A review of models, searches, and constraints

“…Limits from SUSY searches cannot be straightforwardly applied to the scenario under consideration since the pair production cross-section of the scalar mediator field is enhanced by the presence of diagrams with t/u channel exchange of the DM (the corresponding diagrams in SUSY are suppressed since the concerned couplings of the neutralino with quarks and squarks cannot be of O (1)). We have then applied the limits from the dedicated studies [140,284] (see also [285,286]), in which searches of both monojet and dijet + missing energy events have been considered, and reported them in the bottom panel of Fig. 17 (orange region with dashed orange border).…”

Signatures of Majorana dark matter with t-channel mediators

“…A detailed discussion of the conditions that must be fulfilled in order to satisfy the constraints from flavor physics can be found in the Appendix of Ref. 6, for coupling to quarks, and in Ref. 7 for coupling to leptons.…”

“…On the other hand, when the mass difference is moderate, the scalar mediators can be directly pair-produced. 6,12,133,134,[144][145][146][147][148][149] The subsequent decay of the mediator into the dark matter particle and the corresponding quark or lepton leads to signatures with missing transverse momentum and two jets, or with two same-flavor, opposite-charged leptons, respectively. Signatures of this type are being studied extensively in connection to SUSY searches.…”

“…A critical discussion can be found in Ref. 6. A dedicated search for the signals of Majorana dark matter coupling to a light quark has been performed in Ref.…”

Forbidden dark matter at the weak scale via the top portal

“…Instead, we consider "simplified models", effective low-energy theories that capture DM-SM interactions via dimension-4 Lagrangian terms [14][15][16][17][18][19][20][21][22][23][24][25]. In these models the new physics sector usually comprises of no more than the DM state and a mediator.…”