摘要
The Z Zγtriple neutral gauge couplings are absent in the Standard Model(SM)at the tree level.They receive no contributions from dimension-6 effective operators,but can arise from effective operators of dimension-8.We study the scale of new physics associated with such dimension-8 operators that can be probed by measuring the reaction e^+e^-→Zγ followed by Z→■■,vv decays,at future e^+e^- colliders including the CEPC,FCC-ee,ILC and CLIC.We demonstrate how angular distributions of the final-state mono-photon and leptons can play a key rôle in suppressing SM backgrounds.We further demonstrate that using electron/positron beam polarizations can significantly improve the signal sensitivities.We find that the dimension-8 new physics scale can be probed up to the multiTeV region at such lepton colliders.
基金
The work of JE was supported in part by United Kingdom STFC Grant ST/P000258/1
in part by the Estonian Research Council via a Mobilitas Pluss grant
in part by the TDLI distinguished visiting fellow programme
The work of HJH and RQX was supported in part by the National NSF of China(11675086,11835005)
HJH is also supported in part by the CAS Center for Excellence in Particle Physics(CCEPP)
the National Key R&D Program of China(2017YFA0402204)
the Shanghai Laboratory for Particle Physics and Cosmology(11DZ2260700)
the Office of Science and Technology,Shanghai Municipal Government(16DZ2260200)。
