Abstract
We study mono-W signals of dark matter (DM) production at the LHC, in the context of gauge invariant renormalizable models. We analyze two simplified models, one involving an s-channel Z′ mediator and the other a t-channel colored scalar mediator, and consider examples in which the DM-quark couplings are either isospin conserving or isospin violating after electroweak symmetry breaking. While previous work on mono-W signals have focused on isospin violating EFTs, obtaining very strong limits, we find that isospin violating effects are small once such physics is embedded into a gauge invariant simplified model. We thus find that the 8 TeV mono-W results are much less constraining than those arising from mono-jet searches. Considering both the leptonic (mono-lepton) and hadronic (mono fat jet) decays of the W, we determine the 14 TeV LHC reach of the mono-W searches with 3000 fb−1 of data. While a mono-W signal would provide an important complement to a mono-jet discovery channel, existing constraints on these models imply it will be a challenging signal to observe at the 14 TeV LHC.
Highlights
The mono-jet channel provides the most stringent constraints, while mono-W, Z, γ or Higgs signals would provide indispensable complementary information to identify dark matter (DM)
In a recent paper [43] we demonstrated that operators which violate weak gauge symmetries can feature spurious cross section enhancements at LHC energies
For the mono fat jet search, we find that the 8 TeV exclusions are not competitive with existing constraints from mono-jet searches
Summary
The mono-jet channel provides the most stringent constraints, while mono-W , Z, γ or Higgs signals would provide indispensable complementary information to identify DM. The standard list of EFT operators [3, 4] include several which do not respect the weak gauge symmetries of the SM1 Such operators break down at the energies comparable to the electroweak scale, vEW ≈ 246 GeV, rather than the energy scale of new physics, Λ, and are certainly invalid at LHC energies. In a recent paper [43] we demonstrated that operators which violate weak gauge symmetries can feature spurious cross section enhancements at LHC energies This was pertinent for previous mono-W searches for dark matter at the LHC [8, 10, 15], which have largely focused on SU (2) violating EFTs such as [22]. The mono-W process remains an important complementary channel to explore the properties of dark matter
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