Looking for new charged states at the LHC: signatures of magnetic and Rayleigh dark matter

Abstract

Magnetic and Rayleigh dark matter are models describing weak interactions of dark matter with electromagnetism through non-renormalizable operators of dimensions 5 and 7, respectively. Such operators motivate the existence of heavier states that couple to dark matter and are also charged under the electroweak interactions. The recent hints of a gammaray line in the Fermi data suggest that these states may be light enough to be produced at the LHC. We categorize such states according to their charges and decay modes, and we examine the corresponding LHC phenomenology. We emphasize unconstrained models that can be discovered in targeted searches at the upgraded LHC run, while also enumerating models excluded by current data. Generally, models with SU W (2)-singlet states or models where the charged states decay predominantly to tau leptons and/or gauge bosons are still viable. We propose searches to constrain such models and, in particular, find superior performance over existing proposals for some multi-tau final states. Finally, we note several scenarios, especially those dominated by tau final states, that cannot be probed even with 300/fb at LHC14, motivating the further refinement of tau-lepton searches to improve sensitivity to such final states.

LHC constraints on gauge boson couplings to dark matter

“…Numerically, we find that the scale Λ has to satisfy Λ ≳ 510 GeV for m χ ≲ 100 GeV in order to meet the 95% C.L. requirement (4). In the case C B ðΛÞ ¼ 0, C W ðΛÞ ¼ 1, on the other hand, the latest monojet data [20] impose the leading restrictions.…”

“…In order to go beyond the EFT description, one has to specify an ultraviolet (UV) completion, where the operators in (4) arise from a renormalizable theory after integrating out the heavy degrees of freedom mediating the interactions. UV-complete models that generate the operators O B and O W through loops of states charged under Uð1Þ Y and/or SUð2Þ L have been proposed in [3] and their LHC signatures have been studied in [4]. If these new charged particles are light, the high-p T gauge bosons that participate in the E T processes considered here are able to resolve the substructure of the loops.…”

“…the scale where the messenger particles are removed as active degrees of freedom. The DM particle χ can be both a Dirac or a Majorana fermion and The operators introduced in (2) appear in models of Rayleigh DM (see for instance [2][3][4]). They are special in the sense that, up to dimension 7, they are the only effective interactions which lead to velocity-suppressed annihilation rates of DM to photon pairs [5][6][7].…”

The dark penguin shines light at colliders

“…The search for mediator decays in various UV completions of the dipole and Raleigh operators has been studied in [65]. However, since the decay of the mediators only depends on their branching ratios, the information about the DM-mediator coupling is lost in these searches.…”

Dark matter direct detection constraints from gauge bosons loops

“…on the details of the ultraviolet (UV) complete theory. See [42] for a study of LHC signatures that does not rely on the EFT description. Making the above statements precise would require to study a concrete UV completion, which is beyond the scope of the present work.…”