Related papers: Optimal observables for new-physics search at LEP2
In the case of the process $e^+e^-\to\mu^+\mu^-$, we study the sensitivity to either $Z^\prime$ or anomalous gauge coupling effects of two new observables, $\sigma_+$ and $\sigma_-$, conveniently defined for such kind of analysis. We…
We show how the processes $e^- e^+ \to ZH, ~ \gamma H$, which will be studied at LEP2 and at high energy colliders, could be used to search for types of New Physics (NP) characterized by an effective NP scale in the few TeV range and…
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…
We propose a set of precision muon-related observables that serve as a tool to constrain new physics models. Using LEP's precision measurements on the $Z$-boson pole, we derive bounds on the new physics quantum contributions to the decay $Z…
New observables for searching for Z' virtual states in processes e^+e^-\to\bar{f}f are proposed. They are based on the relations following due to renormalizability of an underlying theory between the parameters of the low-energy effective…
The latest preliminary results of the searches for Higgs bosons and Supersymmetric particles at LEP are reviewed. The results include the data-taking in 1999 up to center-of-mass energies of 196 GeV. The combination of the results from the…
New Physics searches at the LHC have increased significantly lower bounds on unknown particle masses. This increases quite dramatically the tension in the interpretation of the data: low energy precision data which are predicted accurately…
We show that in e-e+ colliders at energies above the Z-peak, the process e-e+ to b b(bar) becomes very sensitive to the presence of residual New Physics (NP) effects described by the dim=6 SU(3)*SU(2)*U(1) gauge invariant operators O(qW),…
The preliminary LEP data set on the total cross sections and the forward-backward asymmetries of the $e^+e^-\to\bar{f}f$ processes are analysed to establish a model-independent search for the signals of the virtual Abelian Z' boson. The…
Polarized $\Lambda_b \to \Lambda \gamma$ decays at the Z pole are shown to be well suited for probing a large variety of New Physics effects. A new observable is proposed, the angular asymmetry between the $\Lambda_b$ spin and photon…
Extra neutral gauge bosons suggested by models beyond the standard model can indirectly show up in $e^{+} e^{-}$ collisions through off-resonance deviations of various physical observables from the corresponding standard model values. We…
The theoretical predictions in the standard model (SM) and measurements on the anomalous magnetic dipole moments (MDM) of muon and electron have great precision, hence the MDMs of muon and electron have close relation with the new physics…
We consider whether a discrepancy between the SLAC and LEP measurements of $\Sw$ can be explained by new physics. We find that only the contribution of a new neutral gauge boson, $Z^\prime$, nearly degenerate with the Z can affect the SLAC…
Considering the superior performances of the future e-p colliders, LHeC and FCC-eh, we discuss the feasibility of detecting the extra neutral scalar $h_{2}$ and the light gauge boson $Z^{}_{\mu\tau}$, which are predicted by the…
Expectations for constraints on extra Z bosons are derived for LEP 2 and future linear e+e- colliders. For typical GUTs, a Z' with M_{Z'} \le 3 to 6 \sqrt{s} may cause observable effects. The Z' discovery limits are dominated by statistical…
A search for a Higgs boson produced in e^+e^- collisions in association with a Z boson and decaying into invisible particles is performed. Data collected at LEP with the L3 detector at centre-of-mass energies from 189 GeV to 209 GeV are…
In view of the recent and future electroweak precision data accumulated at LEP and SLC, we systematically analyze possible new physics effects that may occur in the leptonic sector within the context of $SU(2)_R \times SU(2)_L \times…
The combined LEP/SLD data on the b\bar b forward-backward asymmetry from the Z-pole measurements may imply the presence of new physics in the $Zb\bar b$ couplings. In general, the effect of new physics can be parameterized by $SU_C(3)\times…
The many-parametric fit of the LEP2 data on e^+e^-\to e^+e^-, \mu^+\mu^-, \tau^+\tau^- processes is performed to estimate signals of the Abelian Z'-boson beyond the standard model. The model-independent relations between the Z' couplings to…
We study the sensitivity of $ e \gamma$ colliders to physics beyond the Standard Model, when such interactions are natural and their scale lies below the collider energy. Using the reaction $ e \gamma \to b t \nu$ as a specific example, we…