Abstract
We reemphasise the usefulness of angular correlations in LHC searches for missing transverse energy (ETmiss) signatures that involve jet (j) pairs with large invariant mass. For the case of mono-jet production via gluon-fusion, we develop a realistic analysis strategy that allows to split the dark matter (DM) signal into distinct one jet-like and two jet-like event samples. By performing state-of-the-art Monte Carlo simulations of both the mono-jet signature and the standard model background, it is shown that the dijet azimuthal angle difference Delta {phi}_{j_1{j}_2} in 2j + ETmiss production provides a powerful discriminant in realistic searches. Employing a shape fit to Delta {phi}_{j_1{j}_2} , we then determine the LHC reach of the mono-jet channel in the context of spin-0 s-channel DM simplified models. The constraints obtained by the proposed Delta {phi}_{j_1{j}_2} shape fit turn out to be significantly more stringent than those that derive from standard ETmiss shape analyses.
Highlights
dark matter (DM) signal and SM backgoundWhich describe the coupling of a dark sector to the SM through the s-channel exchange of scalar (φ) and pseudoscalar (a) mediators
JHEP02(2019)128 been studied and shown to provide useful information on the structure of the interactions between the dark and the SM sector
By performing simulations of the dark matter (DM) signal taking into account the effects of matrix element matching and merging, parton shower and hadronisation corrections and a realistic detector modelling, we show that the azimuthal angle difference ∆φj1j2 between the two jets in 2j + ETmiss events furnishes a powerful model discriminant in a realistic experimental environment
Summary
Which describe the coupling of a dark sector to the SM through the s-channel exchange of scalar (φ) and pseudoscalar (a) mediators. The DM signal samples are generated at leading order (LO) using the DMsimp [18] implementation of the Lagrangians (2.1) together with MadGraph aMC@NLO [19] and NNPDF3.0 [20] parton distribution functions (PDFs). We consider separately the Z + jets channel with Z → ννand the W + jets mode with W → lν where l = e, μ, τ These backgrounds are generated at LO with MadGraph aMC@NLO and NNPDF3.0 PDFs, and can contain up to two additional jets in the matrix element. Our Z/W + jets samples are normalised such that the different contributions match the number of events in the IM3 signal region as estimated by the ATLAS collaboration scaled to a CM energy of 14 TeV and to the appropriate integrated luminosity. Similar techniques for fast detector simulation are used for the projection studies [34] of the ATLAS collaboration, and have been employed in the phenomenological analyses [15, 17, 35, 36]
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