Speaker
Description
Ref. Front. Phys. 20(1), 015201 (2025) [arXiv:2404.15937, doi:10.15302/frontphys.2025.015201]
Neutral triple gauge couplings (nTGCs) are absent in the Standard Model (SM) and at the dimension-6 level in the Standard Model Effective Field Theory (SMEFT), arising first from dimension-8 operators. As such, they provide a unique window for probing new physics beyond the SM. These dimension-8 operators can be mapped to nTGC form factors whose structure is consistent with the spontaneously-broken electroweak gauge symmetry of the SM. In this work, we study the probes of nTGCs in the reaction
$e^{+}e^{-}\to Z\gamma$ with $Z\to \ell^{+}\ell^{-}(\ell=e,\mu)$ at an $e^{+}e^{-}$ collider. We perform a detector-level simulation and analysis of this reaction at the Circular Electron Positron Collider (CEPC) with collision energy $\sqrt{s}$ = 240 GeV and an integrated luminosity of 20 ab$^{−1}$. We present the sensitivity limits on probing the new physics scales of dimension-8 nTGC operators via measurements of the corresponding nTGC form factors.
Ref. ATLAS-CONF-2025-001
The measurements of the cross sections for 𝑍𝛾 production and the search for neutral triple gauge couplings (nTGC) through $𝑍𝑍\gamma$ or $\gamma^{∗}𝑍\gamma$ vertices are presented, using the full Run2 proton-proton dataset of 140 fb$^{−1}$ produced by the LHC at √𝑠 = 13 TeV and collected by the ATLAS detector. Kinematic distributions are measured using events with a 𝑍 boson candidate decaying into either an 𝑒+𝑒− or 𝜇+𝜇− pair and a photon. The previous results adopted the conventional form factors which only satisfy 𝑈(1) symmetry, which are unphysical, and the overestimation by two orders of magnitude was obtained. Hence, the nTGC form factors satisfying fully $𝑆𝑈(2)_𝐿 \times 𝑈(1)_𝑌$ gauge-invariant symmetry have been proposed. A high photon transverse momentum threshold of 200 GeV, a jet veto selection, and a narrow 𝑍 mass window requirement are applied to define the region of phase space and to optimize the sensitivity to nTGCs, which provide more physically meaningful constraints. The 95% C.L. limits on the nTGC parameters are extracted from the measured differential cross sections, and corrected the overestimation on form factors with the nTGC formulation for the first time at the LHC.
Details
Suggested Speaker:
Dr. Danning Liu Danning.Liu@cern.ch
State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University
| Internet talk | No |
|---|---|
| Is this an abstract from experimental collaboration? | No |
| Name of experiment and experimental site | CEPC and LHC-ATLAS |
| Is the speaker for that presentation defined? | Yes |