Probing Neutral Triple Gauge Couplings with Z^* γ (νν̅γ) Production at Hadron Colliders

We study probes of neutral triple gauge couplings (nTGCs) via Z^*γ production followed by off-shell decays Z^*→νν̅ at the LHC and future pp colliders, including both CP-conserving (CPC) and CP-violating (CPV) couplings. We present the dimension-8 SMEFT operators contributing to nTGCs and derive the correct form factor formulation for the off-shell vertices Z^*γ V^* (V=Z,γ) by matching them with the dimension-8 SMEFT operators. Our analysis includes new contributions enhanced by the large off-shell momentum of Z^*, beyond those of the conventional Zγ V^* vertices with on-shell Zγ. We analyze the sensitivity reaches for probing the CPC/CPV nTGC form factors and the new physics scales of the dimension-8 nTGC operators at the LHC and future 100TeV pp colliders. We compare our new predictions with the existing LHC measurements of CPC nTGCs in the νν̅γ channel and demonstrate the importance of our new method.