Chen Yi, Lykken Joe, Spiropulu Maria, Stolarski Daniel, Vega-Morales Roberto
CERN, European Organization for Nuclear Research, Geneva, Switzerland CH-1211.
Lauritsen Laboratory for High Energy Physics, California Institute of Technology, Pasadena, California 92115, USA.
Phys Rev Lett. 2016 Dec 9;117(24):241801. doi: 10.1103/PhysRevLett.117.241801.
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.
希格斯玻色子与WW和ZZ对的耦合比λ_WZ，是电弱对称破缺中的一个基本参数，也是规范玻色子质量矩阵所具有的（近似）看守对称性的一种度量。我们表明，希格斯玻色子衰变为四个轻子，通过树图水平或单圈干涉效应，对λ_WZ的大小，特别是其整体符号敏感。确定这个符号需要干涉效应，因为仅通过速率信息几乎无法测量。此外，简单地确定符号实际上就确定了希格斯玻色子的看守表示。我们发现，h→4ℓ（4ℓ≡2e2μ、4e、4μ）衰变在高亮度13 TeV大型强子对撞机上有直接确定整体符号的良好前景。我们还研究了大型强子对撞机对h→4ℓ中λ_WZ大小的最终灵敏度。我们的结果独立于希格斯玻色子耦合的其他测量，特别是很大程度上不依赖于也在单圈中出现的顶夸克汤川耦合的假设。这使得h→4ℓ成为电弱对称破缺和看守对称性的独特且独立的探针。
