LHC constraints on gauge boson couplings to dark matter

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LHC constraints on gauge boson couplings to dark matter

Andreas Crivellin, Ulrich Haisch, and Anthony Hibbs

Phys. Rev. D 91, 074028 – Published 28 April 2015

Abstract

Collider searches for energetic particles recoiling against missing transverse energy $(E_{T})$ allow us to place strong bounds on the interactions between dark matter (DM) and standard model (SM) particles. In this article we update and extend LHC constraints on effective dimension-7 operators involving DM and electroweak gauge bosons. A concise comparison of the sensitivity of the monophoton, mono- $W$ , mono- $Z$ , mono- $W / Z$ , and invisible Higgs-boson decays in the vector boson fusion mode and the monojet channel is presented. Depending on the parameter choices, either the monophoton or the monojet data provide the most stringent bounds at the moment. We furthermore explore the potential of improving the current 8 TeV limits at 14 TeV. Future strategies capable of disentangling the effects of the different effective operators involving electroweak gauge bosons are discussed as well.

Received 20 January 2015

DOI:https://doi.org/10.1103/PhysRevD.91.074028

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Authors & Affiliations

Andreas Crivellin^1,*, Ulrich Haisch^2,1,†, and Anthony Hibbs^2,‡

¹CERN Theory Division, CH-1211 Geneva 23, Switzerland
²Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PN, United Kingdom

^*andreas.crivellin@cern.ch
^†u.haisch1@physics.ox.ac.uk
^‡Anthony.Hibbs@physics.ox.ac.uk

Article Text

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Issue

Vol. 91, Iss. 7 — 1 April 2015

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Images

Figure 1
Representative examples of graphs that generate a $E_{T} + γ$ , $E_{T} + Z (\to ℓ^{+} ℓ^{-})$ , $E_{T} + W / Z (\to j)$ or $E_{T} + 2 j$ signal. The operator insertions are indicated by yellow squares while SM vertices are represented by black dots. Propagators labeled by $V$ include all possible photon, $Z$ -boson or $W$ -boson exchanges. See text for further details.
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Figure 2
Assortment of LHC bounds on the new-physics scale $Λ$ , assuming $C_{B} (Λ) = 1$ , $C_{W} (Λ) = 0$ (upper panel) and $C_{B} (Λ) = 0$ , $C_{W} (Λ) = 1$ (lower panel). In both cases the DM particles are taken to be Dirac and $C_{\tilde{B}} (Λ) = C_{\tilde{W}} (Λ) = 0$ . The colored curves correspond to the limits arising from the latest monophoton (red), $E_{T} + Z (\to ℓ^{+} ℓ^{-})$ (orange), $E_{T} + W (\to μ ν_{μ})$ (yellow), $E_{T} + W / Z (\to hadrons)$ (purple), monojet (blue) and VBF $h \to invisible$ (grey) searches. The width of the bands reflect the associated scale uncertainties.
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Figure 3
Limits on $Λ$ in the $C_{B} (Λ)$ – $C_{W} (Λ)$ plane. The different panels correspond to the monophoton (upper left), $E_{T} + Z (\to ℓ^{+} ℓ^{-})$ (upper middle), $E_{T} + W (\to μ ν_{μ})$ (upper right), $E_{T} + W / Z (\to hadrons)$ (lower left), monojet (lower middle) and VBF $h \to invisible$ (lower right) search. All results employ $m_{χ} = 100 GeV$ and $C_{\tilde{B}} (Λ) = C_{\tilde{W}} (Λ) = 0$ . The contour labels indicate the value of the new-physics scale in units of GeV.
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Figure 4
Combination of the bounds on the new-physics scale in the $C_{B} (Λ)$ – $C_{W} (Λ)$ plane, employing $m_{χ} = 100 GeV$ and $C_{\tilde{B}} (Λ) = C_{\tilde{W}} (Λ) = 0$ . In the upper panel the search strategy that provides the leading constraint is indicated by the superimposed numbers, with 1 (5) representing the latest monophoton (monojet) search, while the lower panel shows the resulting contours of constant $Λ$ in units of GeV.
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Figure 5
Azimuthal angle distributions at the 14 TeV LHC. The signal curves correspond to $C_{B} (Λ) = 0$ , $C_{W} (Λ) = 1$ (red) and $C_{\tilde{B}} (Λ) = 0$ , $C_{\tilde{W}} (Λ) = 1$ (blue), and both use $Λ = 1 TeV$ and $m_{χ} = 100 GeV$ . For comparison the prediction of the dominant SM background process $p p \to Z (\to \bar{ν} ν) + 2 j$ (black) employing the same event selection criteria is shown as well.
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Figure 6
Normalized $Δ ϕ_{j_{1} j_{2}}$ distributions for $300 {fb}^{- 1}$ (upper panel) and $3000 {fb}^{- 1}$ (lower panel) of 14 TeV LHC data. The red (blue) histogram shows the signal plus background prediction for $O_{W}$ ( $O_{\tilde{W}}$ ). The grey bar chart represents the expected SM background, which for better visibility, has been rescaled by a factor of $1 / 3$ . The solid curves indicate the best fits of the form $a_{0} + a_{1} \cos Δ ϕ_{j_{1} j_{2}} + a_{2} \cos (2 Δ ϕ_{j_{1} j_{2}})$ . See text for additional explanations.
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