Higgs mechanism and loop-induced decays of a scalar into two Z bosons

Qing Hong Cao*, C. B. Jackson, Wai Yee Keung, Ian Low, Jing Shu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


We discuss general on-shell couplings of a scalar with two Z bosons using an operator analysis. In addition to the operator that originated from the Higgs mechanism, two dimension-five operators, one CP even and one CP odd, are generated only at the loop level. Simple formulas are derived for the differential decay distributions when the Z pair subsequently decays into four leptons by computing the helicity amplitudes, from which it is shown the CP-odd operator merely induces a phase shift in the azimuthal angular distribution between the two decay planes of the Z bosons. We also investigate new physics scenarios giving rise to loop-induced decays of a scalar into the ZZ pair, and argue that the total decay width of such a scalar would be an order-of-magnitude smaller than that of a Higgs boson, should such decays be observed in the early running of the LHC. Therefore, the total decay width alone is a strong indicator of the Higgs nature, or the lack thereof, of a scalar resonance in ZZ final states. In addition, we study the possibility of using the azimuthal angular distribution to disentangle effects among all three operators.

Original languageEnglish (US)
Article number015010
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number1
StatePublished - Jan 20 2010

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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