A novel approach to probing new physics with neutral Gauge Boson couplings
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. Editorial .
February 2021 Vol. 64 No. 2: 221061 https://doi.org/10.1007/s11433-020-1633-x
Editor’s Focus
Editor’s Focus
A novel approach to probing new physics with neutral Gauge Boson couplings Even before reaching the energy threshold for producing any new elementary particle beyond the Standard Model (SM) [1], new physics effects can be systematically described by effective operators with mass-dimensions higher than 4. These new operators together with the SM form the so-called SM effective theory (SMEFT). Most analyses consider only dimension-6 operators. However, these do not contribute to neutral triple gauge couplings (nTGCs), which first arise from dimension-8 operators [2]. Hence, precision probes of nTGCs at future e+ e− colliders will provide a unique window to the possible new physics beyond the SM. Three theorists recently proposed [3] a novel approach to probing nTGCs at planned future e+ e− colliders [4], including the CEPC, FCC-ee, ILC, and CLIC. They constructed a new set of pure gauge operators of dimension-8 that contribute to nTGCs and are independent of the dimension-8 operator involving Higgs doublets. They found that such pure gauge operators generate both ZγZ ∗ and Zγγ∗ vertices with rapid energy dependence ∝ E 5 , and can be probed sensitively via the reaction e− e+ → Zγ . They demonstrated [3] that measuring the nTGCs via the reaction e+ e− → Zγ with hadronic decays Z → qq¯ can probe the new physics scale of dimension-8 pure gauge operator OG+ up to the range 1-5 TeV at the CEPC, FCC-ee and ILC colliders √ √ with s=(0.25-1) TeV, and up to the range 10-16 TeV at CLIC with s=(3-5) TeV (cf. Table 3 and Figure 8 of ref. [3]). These sensitivities are compared with those of the dimension-8 nTGC operator Oe (involving Higgs doublets) and the related BW dimension-8 fermionic contact operator OC+ (contributing to the e− e+ Zγ vertex). The sensitivity reaches of the nTGC new physics scale as established in ref. [3] are substantially stronger than what the authors found previously [5] for the Higgs-related nTGC operator Oe via Z decays into leptonic channels. This study [3] BW demonstrates the importance of probing the nTGCs from dimension-8 operators via the reaction e+ e− → Zγ, with sensitivity reaches of the corresponding new physics scales extending well into the multi-TeV regime. It provides a distinctive modelindependent benchmark for new physics searches at e+ e− colliders being planned [4] and strongly motivates further detector level simulations for probing the nTGCs. Rong-Gen Cai Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China 1 J. Ellis, Int. J. Mod. Phys. A 33, 1830003 (2018); arXiv: 1810.11263. 2 G. J. Gounaris, J. Layssac, and F. M. Renard, Phys. Rev. D 65, 017302 (2001); Phys. Rev. D 62, 073012 (2000), arXiv: hep-ph/0005269. 3 J. Ellis, H.-J. He, and R.-Q. Xiao, Sci. China-Phys. Mech. Astron. 64,
c Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 ⃝
221062 (2021). 4 F. An, et al. (CEPC Study Group), arXiv: 1811.
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