title: Golden Probe of Electroweak Symmetry Breaking.
abstract: The ratio of the Higgs couplings to WW and ZZ pairs, λ_{WZ}, is a fundamental parameter in electroweak symmetry breaking as well as a measure of the (approximate) custodial symmetry possessed by the gauge boson mass matrix. We show that Higgs decays to four leptons are sensitive, via tree level or one-loop interference effects, to both the magnitude and, in particular, overall sign of λ_{WZ}. Determining this sign requires interference effects, as it is nearly impossible to measure with rate information. Furthermore, simply determining the sign effectively establishes the custodial representation of the Higgs boson. We find that h→4ℓ (4ℓ≡2e2μ, 4e, 4μ) decays have excellent prospects of directly establishing the overall sign at a high luminosity 13 TeV LHC. We also examine the ultimate LHC sensitivity in h→4ℓ to the magnitude of λ_{WZ}. Our results are independent of other measurements of the Higgs boson couplings and, in particular, largely free of assumptions about the top quark Yukawa couplings which also enter at one loop. This makes h→4ℓ a unique and independent probe of electroweak symmetry breaking and custodial symmetry.
authors.affiliation: CERN, European Organization for Nuclear Research, Geneva, Switzerland CH-1211.|Lauritsen Laboratory for High Energy Physics, California Institute of Technology, Pasadena, California 92115, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Theoretical Physics Department, Fermilab, P.O. Box 500, Batavia, Illinois 60510, USA.
authors.forename: Joe
authors.initials: J
authors.lastname: Lykken
authors.affiliation: Lauritsen Laboratory for High Energy Physics, California Institute of Technology, Pasadena, California 92115, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Spiropulu
authors.affiliation: Ottawa-Carleton Institute for Physics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Stolarski
authors.affiliation: Departamento de Física Teórica y del Cosmos and CAFPE, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Vega-Morales