Related papers: New Physics Off the $Z$-Pole: $e^+ e^- \rightarrow…
The measurement of the charge asymmetry $A_{FB}(e^-e^+\to \mu^-\mu^+)$ will play an important role at the high-luminosity circular electron-positron collider FCCee considered for construction at CERN. In particular, near the Z resonance,…
We examine the possibility to detect new SM-neutral vector bosons ($Z'$) that couple exclusively to leptons in the electron-positron mode of the Future Circular Collider (FCC-ee). Focusing on the $Z'$ production with a radiated photon…
While electron and muon dipole moments are well-established precision probes of physics beyond the standard model, it is notoriously challenging to test realistic new-physics (NP) scenarios for the $\tau$ lepton. Constructing suitable…
The determination of the $Zb\bar{b}$ coupling in experiments has been a long-standing challenge, as the limited precision of off $Z$-pole measurements at the LEP has resulted in two degenerate solutions remained to be resolved. In this…
LEP and SLC provide accurate data on the process (e^+e^- -> f bar f) at the Z resonance. The GigaZ option at a future linear e^+e^- collider (ILC) will further improve these measurements. As a consequence, theory predictions with…
A confirmation of the long-standing muon $g$-2 discrepancy requires both experimental and theoretical progress. On the theory side, the hadronic corrections are under close scrutiny, as they induce the leading uncertainty of the Standard…
The main possibilities of investigation of leptons and bosons production in interaction of polarized photons are considered. The usage of $\gamma\gamma\to f\bar{f}[+\gamma]$ reactions for the luminosity measurement on linear photon collider…
If all new particles are too heavy to be directly produced in the future Colliders, then the long sought New Physics (NP) could only appear in the form of new interactions, beyond those of the Standard Model (SM). Many of the processes that…
The past ten years of physics with e+e- colliding experiments at LEP and SLAC have shown the success of these experiments on not only impressively proving the theoretical predictions of the Standard Model (SM), but also to help provide…
We present a set of studies concerning the description of New Physics (NP) effects caracterized by a scale much higher than the electroweak scale. We show that both present experimental results and several types of theretical considerations…
The expected experimental precision of the rates and asymmetries in the Future Circular Collider with electron positron beams (FCC-ee) in the centre of the mass energy range 88-365GeV considered for construction in CERN, will be better by a…
The $ZZ\gamma$ triple 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…
Extending the Standard Model (SM) with sterile ('right-handed') neutrinos is one of the best motivated ways to account for the observed neutrino masses. We discuss the expected sensitivity of future lepton collider experiments for probing…
New CP-violating asymmetries of decay leptons in $e^+\,e^-\;\ra\;t\,\bar{t}$, arising from electric and weak dipole couplings of $t\,\bar{t}$ to $\gamma$ and $Z$, are examined in the case of unpolarized and longitudinally polarized…
At a future linear collider, a polarized electron beam will play an important role in interpreting new physics signals. Backgrounds to a new physics reaction can be reduced by choice of the electron polarization state. The origin of a new…
The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the $e^{+}e^{-}$ Future Circular Collider (FCC-$e^{+}e^{-}$) for Z and WW physics at 45 and 80 GeV beam energy respectively.…
The effects of new neutral $Z^\prime$ boson in $B_{s}\to\phi\ell^{+}\ell^{-}$, when $\phi$ is longitudinal or transverse polarized, are studied. In addition, the implications of $Z^{\prime}$ boson on the unpolarized and polarized $CP$…
We study the diagnostic power of future $e^+e^-$ colliders with ${\sqrt {s}} = 500$ GeV (the New Large Collider ($NLC$)) for a model independent determination of the $Z'$ gauge couplings to quarks and leptons. The interference of the $Z'$…
The possible form of New Physics (NP) interactions affecting the ZZZ, $ZZ \gamma$ and $Z\gamma \gamma$ vertices, is critically examined. Their signatures and the possibilities to study them, through ZZ and $Z\gamma$ production, at the…
We present projections for the sensitivity of future high-energy colliders to new physics through precision measurements of the Standard Model (SM) interactions, focusing on near-term electron-positron facilities: FCC-ee, LEP3, and the…