The 2023 International Workshop on the High Energy Circular Electron Positron Collider

SMEFT offers a systematic methodology within the reachable energy scale for exploring the potential manifestations of new physics beyond the SM. Electroweak dipole operators in the SMEFT are noteworthy probes for BSM effects, but usually ignored before in the cases under the top quark mass due to the suppression by particle mass over the possible large NP energy scale, such as in the...

I will discuss results from [[2203.04828][1]], in which we explore the potential impact of electroweak and Higgs precision measurements at future electron-positron colliders, including the CEPC, on several typical supersymmetric models, including the Constrained Minimal Supersymmetric Standard Model (CMSSM), Non-Universal Higgs Mass generalisations (NUHM1, NUHM2), and the 7-dimensional Minimal...

The gauged $U(1)_{L_\mu - L_\tau}$ model is a candidate model for explaining the muon g-2 anomaly because the $Z'$ in the model has a natural normal coupling to muon. Due to other experimental data constraints the viable mass range for the usual $Z'$ is constrained to be lower than a few hundred MeV. It has been shown that if the $Z'$ has a maximal off-diagonal mixing, $(\bar \mu \gamma^\mu...

Abstract: The QCD-like dark sector with GeV-scale dark hadrons has the potential to
generate new signatures at the Large Hadron Collider (LHC). In this paper, we consider
a singlet scalar mediator in the tens of GeV-scale that connects the dark sector and the
Standard Model (SM) sector via the Higgs portal. We focus on the Higgs-strahlung process,
qq
0 → W∗ → W H, to produce a highly...

In this work, we explore the potential of probing the inelastic dark matter (DM) model with
an extra U(1)D gauge symmetry at the Large Hadron Collider, ForwArd Search ExpeRiment and
Super Tau Charm Factory. To saturate the observed DM relic density, the mass splitting between
two light dark states has to be small enough, and thus leads to some distinctive signatures at these
colliders. By...

We study probes of neutral triple gauge couplings (nTGCs) at the LHC, CEPC and SPPC. The nTGCs provide a unique window to the new physics beyond the Standard Model (SM) because they can arise from SM effective field theory (SMEFT) operators that respect the full electroweak gauge group $\mathrm{SU(2)}_{\mathrm L}^{}\!\otimes\mathrm{U(1)}_{\mathrm Y}^{}$ of the SM only at the level of...

The proposed CEPC serves as a Higgs factory and provides a unique opportunity to explore new physics related to dark matter. We present a set of Lorentz invariant kinematic variables that effectively reconstruct the mass of semi-invisible decaying particle pairs at lepton colliders, enhancing the signal's statistical significance. Applying these variables to smuon pair production at a 240 GeV...

We show that testing Bell inequalities in $W^\pm$ pair systems by measuring their angular correlation suffers from the ambiguity in kinetical reconstruction of the di-lepton decay mode. We further propose a new set of Bell observables based on the measurement of the linear polarization of the $W$ bosons, providing a realistic observable to test Bell inequalities in $W^\pm$ pair systems for...

The neutral triple gauge couplings are absent in the Standard Model Effective Field Theory up to dimension-6 but could arise from dimension-8 operators. This study is performed based on the latest formulation with brand new fully gauge invariant treatment applied, and will focus on the measurement of pure gauge dimension-8 operators and set exclusive limits on its Wilson coefficients at 95%...

The exotic Z decays to a QCD-like dark sector provide unexplored opportunities at colliders. In this talk, we explore the region where the Z portal is generated by a dark Z′. The phenomenological signatures of light Z' are studied, with the produced dark hadrons regarded as long-lived particles. Both dark shower signals in exotic Z decays and FCNC decays of B hadrons are taken into account.