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Title: On the interpretation of a possible ~ 750 GeV particle decaying into γγ

We consider interpretations of the recent ~3σ reports by the CMS and ATLAS collaborations of a possible X(~ 750 GeV) state decaying into yy 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 2/3 T quark, a doublet of vector-like quarks (T;B), and a vector-like generation of quarks, with or without leptons that also contribute to the X → yy decay amplitude. We also consider the possibility that X(750) 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 X particle and the heavy vector-like fermions are small enough to be perturbative so long as the X particle has dominant decay modes into gg and yy. In conclusion, the decays X → ZZ,Zy and W+W- are interesting prospective signatures that may help distinguish between different vector-like fermion scenarios.
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. King's College London, London (United Kingdom); European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. King's College London, London (United Kingdom)
  4. Univ. of Sussex, Brighton (United Kingdom)
  5. Univ. of Cambridge, Cambridge (United Kingdom)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 3; Journal ID: ISSN 1029-8479
Springer Berlin
Research Org:
Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS Beyond Standard Model; Higgs Physics; Technicolor and Composite Models