Abstract
A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. This search uses jet substructure techniques to identify hadronically decaying vector bosons in both Lorentz-boosted and resolved scenarios. This analysis yields improvements of 80% in terms of excluded signal cross sections with respect to the previous CMS analysis using the same data set. No significant excess with respect to the standard model expectation is observed and limits are placed on the parameter space of the simplified models. Mediator masses between 80 and 400 GeV in the scalar and pseudoscalar models, and up to 1.5 TeV in the vector and axial vector models, are excluded.
Highlights
Background estimationThe presence of dark matter (DM) production would be observable as an excess of events above SM backgrounds at high ETmiss
The background shapes in this second fit are allowed to vary within their uncertainties, which are propagated from the fit to the control region data, described in the previous section, accounting for correlations between the control region fit parameters
A search has been presented for an excess of events with at least one energetic jet in association with large ETmiss in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV
Summary
The CMS detector, described in ref. [26], is a multi-purpose apparatus designed to study high-transverse momentum (pT) products of energetic proton-proton and heavy-ion collisions. The CMS muon system consists of gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid, covering |η| < 2.4. The first level of the CMS trigger system, composed of specialized hardware processors, is designed to select the most interesting events in less than 4 μs, using information from the calorimeters and the muon detectors. The particle-flow (PF) algorithm reconstructs and identifies each individual particle with an optimized combination of information from the various elements of the CMS detector [27, 28]. The missing transverse momentum vector pTmiss is defined as the negative vector sum of the pT of all final state particles that are reconstructed using the PF algorithm [33]. Events with a large misreconstructed ETmiss are removed by applying quality filters on the tracker, ECAL, HCAL, and muon detector data
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