paper

On the Interpretation of a Possible GeV Particle Decaying into

arXiv:1512.05327 · doi:10.1007/JHEP03(2016)176

Abstract

We consider interpretations of the recent reports by the CMS and ATLAS collaborations of a possible state decaying into final states. We focus on the possibilities that this is a scalar or pseudoscalar electroweak isoscalar state produced by gluon-gluon fusion mediated by loops of heavy fermions. We consider several models for these fermions, including a single vector-like charge T quark, a doublet of vector-like quarks , and a vector-like generation of quarks, with or without leptons that also contribute to the decay amplitude. We also consider the possibility that is a dark matter mediator, with a neutral vector-like dark matter particle. These scenarios are compatible with the present and prospective direct limits on vector-like fermions from LHC Runs 1 and 2, as well as indirect constraints from electroweak precision measurements, and we show that the required Yukawa-like couplings between the particle and the heavy vector-like fermions are small enough to be perturbative so long as the particle has dominant decay modes into and . The decays and are interesting prospective signatures that may help distinguish between different vector-like fermion scenarios.

36 pages, 7 figures. V2: typos corrected, references added, version submitted to journal. V3: Version accepted by JHEP

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