Abstract
Results are presented from a search for new decaying massive particles whose presence is inferred from an imbalance in transverse momentum and which are produced in association with a single top quark that decays into a bottom quark and two light quarks. The measurement is performed using 19.7 fb^{-1} of data from proton-proton collisions at a center-of-mass energy of 8TeV, collected with the CMS detector at the CERN LHC. No deviations from the standard model predictions are observed and lower limits are set on the masses of new invisible bosons. In particular, scalar and vector particles, with masses below 330 and 650GeV, respectively, are excluded at 95% confidence level, thereby substantially extending a previous limit published by the CDF Collaboration.
Highlights
Extensions of theories beyond the standard model (BSM), such as those with universal extra dimensions [1] or supersymmetry [2,3], predict the existence of neutral massive particles that are “invisible,” that is, they interact only weakly with matter
Such particles can be produced in collider experiments, but escape detection so that their existence can only be inferred by the presence of a large imbalance in transverse momentum (EmT iss)
These searches have not revealed any evidence for BSM monojet or monophoton final states, but this nonobservation can be accommodated in a theory where the new particles change the quark flavor and convert a light quark to a top quark
Summary
Extensions of theories beyond the standard model (BSM), such as those with universal extra dimensions [1] or supersymmetry [2,3], predict the existence of neutral massive particles that are “invisible,” that is, they interact only weakly with matter. The BSM event signature would not correspond to monojet or monophoton final states, but to events containing single top quarks and large EmT iss, referred to as “monotop” candidates. In this Letter, we present a search for such events in which an invisible BSM particle is produced in association with a top quark [10,11,12,13,14,15,16,17,18,19,20].
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