Abstract
A search for new physics in events with a Z boson produced in association with large missing transverse momentum at the LHC is presented. The search is based on the 2016 data sample of proton-proton collisions recorded with the CMS experiment at sqrt{s} = 13,text {TeV} , corresponding to an integrated luminosity of 35.9,text {fb}^{-1}. The results of this search are interpreted in terms of a simplified model of dark matter production via spin-0 or spin-1 mediators, a scenario with a standard-model-like Higgs boson produced in association with the Z boson and decaying invisibly, a model of unparticle production, and a model with large extra spatial dimensions. No significant deviations from the background expectations are found, and limits are set on relevant model parameters, significantly extending the results previously achieved in this channel.
Highlights
In the pursuit of new physics at the CERN LHC, many scenarios have been proposed in which production of particles that leave no trace in collider detectors is accompanied by production of a standard model (SM) particle, which balances the transverse momentum in an event
Processes that were found to have a negligible contribution to the signal region include: W+jets, because of the very low probability for a jet to be reconstructed as a lepton and the dilepton system to be within the Z boson mass window; the SM process Z(→ )H(→ ZZ → 4ν), which is a subset of the ZH(inv.) signal and accounts for 0.1% of SM Higgs boson decays; and gg → H(→ WW), which has similar topology to continuum WW production but makes a negligible contribution after the full selection
The background estimate for these processes is improved by selecting control regions (CRs) with alternative decay modes that provide a normalization based on CRs in data, and probe the lost-boson pT distribution, which is expected to be independent of the decay mode
Summary
In the pursuit of new physics at the CERN LHC, many scenarios have been proposed in which production of particles that leave no trace in collider detectors is accompanied by production of a standard model (SM) particle, which balances the transverse momentum in an event. Models [21,22,23] construct a generic connection between SM and DM particles via a Higgs boson mediator This analysis considers decays into invisible particles of an SM-like Higgs boson produced in association with a Z boson, as shown in Fig. 1 (lower left). Another popular BSM paradigm considered here is the Arkani-Hamed–Dimopoulos–Dvali (ADD) model with large extra spatial dimensions [24,25,26], which is motivated by the hierarchy problem, i.e., the disparity between the electroweak unification scale (MEW ∼ 1 TeV) and the Planck scale (MPl ∼ 1016 TeV).
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