Search for dark matter in events with heavy quarks and missing transverse momentum in $$pp$$ p p collisions with the ATLAS detector

Abstract

This article reports on a search for dark matter pair production in association with bottom or top quarks in of collisions collected at TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing -quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter–nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.

LHC constraints on gauge boson couplings to dark matter

“…The efficiencies that we find amount to around 70% for the monophoton signal, 60% in both the mono-Z and mono-W case and 65% for the mono-W=Z signature. These findings agree with [15] for the E T þ γ, [11] for the E T þ Z, [13] for the E T þ W and [16] for the E T þ W=Z signal. For the monojet signal and the search for invisible decays of the Higgs boson in the VBF channel, we find reconstruction efficiencies in the ballpark of 95%.…”

“…In the case of the E T þ Zð→ l þ l − Þ search channel, we use the ATLAS results [11] that utilize 20.3 fb −1 of 8 TeV data. The selection criteria relevant to our analysis are p T;l > 20 GeV; jη l j < 2.5; m ll ∈ ½76; 106 GeV;…”

“…The ATLAS search [16] looks for a E T þ W=Z signal, where the W or Z boson decays hadronically. This analysis is based on 20.3 fb −1 of 8 TeV data; jet candidates are reconstructed using the Cambridge/Aachen (C/A) algorithm [22] with a radius parameter R ¼ 1.2 and subjected to a mass-drop filtering procedure [23].…”

“…While the sensitivity of future direct detection experiments may allow us to set novel bounds on the Wilson coefficients C B ðΛÞ and C W ðΛÞ for heavy DM particles with m χ ≳ 1 TeV once loop effects are taken into account [8], in the case of light DM the leading [and for CBðΛÞ and CWðΛÞ the only] restrictions arise and will continue to arise from collider searches involving large amounts of E T . In fact, the DM-SM interactions (2) have been constrained using 7 TeV and 8 TeV LHC data on invisible decays of the Higgs boson in the vector boson fusion (VBF) mode [9] as well as the E T þ Z [10,11], monophoton [12] and E T þ W [13] channels.…”

“…First, to update the existing constraints by taking into account the latest monophoton [14,15], E T þ W=Zð→ hadronsÞ [16] and VBF h → invisible [17] searches. Second, to extend the studies [9][10][11][12][13] by considering in addition the E T þ Wð→ leptonsÞ channel [18,19] as well as the newest monojet data [20]. An assortment of Feynman diagrams that lead to the E T signatures investigated in the following are displayed in Fig.…”