Related papers: Model-independent constraints on contact interacti…
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…
The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no…
Physics from beyond the Standard Model can induce four fermion operators involving a quark, an anti-quark, a lepton and an anti-lepton. The coefficients of these operators can be constrained by various observations. We update the bounds…
All couplings of a new heavy gauge boson to ordinary fermions can be determined in a model-independent way at a large $e^+e^-$ collider for large enough statistics. No such determination is possible at LEP 200, however, because its design…
Preliminary results of measurements of fermion-pair production at LEP2 are used to derive limits on new physics phenomena. Combinations of the cross sections and asymmetrie of the 4 LEP collaborations are interpreted in terms four-fermion…
Very recently, we proposed an explanation of the discrepancy between the measured anomalous magnetic moment of the muon and the Standard Model (SM) prediction in which the dominant contribution to $(g-2)_\mu$ originates in Kaluza-Klein (KK)…
We present a phenomenological constraint on a pseudovector light boson beyond the Standard Model, which can induce a long-range spin-dependent interaction $\alpha^{\prime\prime}({\bf s}_1\cdot{\bf s}_2)\,{\rm e}^{-\lambda r}/r$. In the…
We obtain bounds on the mass scales characterizing four-fermion contact interactions in charged current processes. The bounds arise from the Q^2 and x distributions in the processes e p -> \nu X measured by the two HERA experiments, H1 and…
Single- and multi-photon events with missing energy are selected in 619/pb of data collected by the L3 detector at LEP at centre-of-mass energies between 189GeV and 209GeV. The cross sections of the process e^+e^- -> nu nu gamma (gamma) are…
We reconsider the bounds on non-standard neutrino interactions with matter which can be derived by constraining the four-charged-lepton operators induced at the loop level. We find that these bounds are model dependent. Naturalness…
Non-standard scenarios described by effective contactlike interactions can be revealed only by searching for deviations of the measured observables from the Standard Model (SM) predictions. If deviations were indeed observed within the…
Using effective-lagrangian techniques we perform a systematic survey of the lowest-dimension effective interactions through which heavy physics might manifest itself in present experiments. We do not restrict ourselves to special classes of…
The study of lepton pair production is a powerful test of the Standard Model (SM) and can be used to search for phenomena beyond the SM. New heavy neutral bosons $Z'$ decaying to charged lepton pairs $l^+l^-$ ($l=e, \mu$) are predicted by…
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…
A complete set of dimension-6 effective contact interactions involving Higgs, gauge bosons and quarks is studied. Limits on the coefficients of these new operators are obtained from the experimental values of the $Z$ and $W$ gauge bosons…
We discuss the possibility of explaining the excess in the cross section at high-Q^2 recently found at HERA in terms of four-fermion effective interactions. To avoid the constraints from low-energy data, we select three special cases in…
We consider the possibility of experimental observation of flavor-diagonal and helicity conserving contact terms in the four fermion reactions e^+ e^- -> e^+ e^- \mu^+ \mu^- and e^- q -> e^- \mu^+ \mu^- q at LEP2 and HERA.
We reexamine the contact interaction hypothesis for excess high-$Q^2$ events seen at HERA in $e^+ p \to e^+ X$ scattering. We consider the most general structure of contact interactions insisting on $SU(3)_C\times SU(2)_L \times U(1)_Y$…
Deep-inelastic e^\pm p scattering at high squared momentum transfer Q^2 up to 30000 GeV^2 is used to search for eq contact interactions associated to scales far beyond the HERA centre of mass energy. The neutral current cross section…
A contact interaction analysis is presented to search for new phenomena beyond the Standard Model in deep inelastic $e^\pm p \rightarrow e^\pm \, hadrons$ scattering. The data are collected with the H1 detector at HERA and correspond to…