Universal and Non Universal New Physics Effects in a General Four-fermion Process: a Z-peak Subtracted Approach

We calculate, using a Z-peak subtracted representation of four-fermion processes previously illustrated for the case of electron-positron annihilation into charged lepton-antilepton, the corresponding expressions of the new physics contributions for the case of final quark-antiquark states, allowing the possibility of both universal and non universal effects. We show that, in each case, the main result obtained for the final lepton channel can be generalized, so that every experimentally measurable quantity can be expressed in terms of input parameters \underline{measured} on Z resonance, of $\alpha(0)$ and of a small number of subtracted one loop expressions. Some examples of models are considered for several c.m. energy values, showing that remarkable simplifications are often introduced by our approach. In particular, for the case of a dimension-six lagrangian with anomalous gauge couplings, the same reduced number of parameters that would affect the observables of final leptonic states are essentially retained when one moves to final hadronic states. This leads to great simplifications in the elaboration of constraints and, as a gratifying byproduct, to the possibility of making the signal from these models clearly distinguishable from those from other (both universal and non universal) competitors.Comment: 21 pages + 3 figures in ps file, corrected version. (e-mail [email protected]

Signals for Neutralino Box Effects at LEP2

We have computed the contribution to the observables of the final two fermion channel at LEP2, at the limiting energy $\sqrt{q^2}=200 GeV$, coming from boxes with two neutralinos of purely gaugino type, of mass $M=100 GeV$. We find a potentially visible effect only for the muon channel, in the cross section and, to a lesser extent, in the forward-backward asymmetry. Analogous effects coming from the chargino box are also briefly discussed.Comment: 10 pages and 2 figures. e-mail: [email protected]

Constraints on anomalous gauge couplings from present LEP1 and future LEP2, BNL data

We analyze, in a rather general model where anomalous triple gauge couplings are present, the visible effects in R$_b$ (measured at LEP1), in W pair production (to be measured at LEP2) and in the muon anomalous magnetic moment (to be measured at BNL). From the combination of the three experiments a remarkable improvement on the pure LEP2 constraints is obtained.Comment: 10 pages and 6 figures. e-mail: [email protected]

Logarithmic Fingerprints of Virtual Supersymmetry

We consider the high energy behaviour of the amplitudes for production of leptons, quarks, Higgs bosons, sleptons, squarks, gauge bosons, charginos, neutralinos. We concentrate our discussion on the universal (process independent) logarithmic terms which factorize the Born amplitude and which are typically of the form [a ln(s/m^2)-ln^2(s/m^2)]. We perform a systematic determination of the coefficient "a" for the various final states and we emphasize the striking features which differentiate the SM and the MSSM cases. We show that a comparison with experiments at future colliders should provide a clean way to test the gauge and Higgs structures of the electroweak interactions owing to the presence of sizeable (visible) virtual logarithmic supersymmetric contributions.Comment: 11 pages e-mail: [email protected]

New Physics signals from measurable polarization asymmetries at LHC

We propose a new type of Z polarization asymmetry in bottom-Z production at LHC that should be realistically measurable and would provide the determination of the so-called $A_b$ parameter, whose available measured value still appears to be in disagreement with the Standard Model prediction. This polarization can be measured independently of a possible existence of Supersymmetry. If Supersymmetry is found, a second polarization, i.e. the top longitudinal polarization in top-charged Higgs production, would neatly identify the $\tan \beta$ parameter. In this case, the value of $A_b$ should be in agreement with the Standard Model. If Supersymmetry does not exist, a residual disagreement of $A_b$ from the Standard Model prediction would be a clean signal of New Physics of "non Supersymmetric" origin.Comment: typo correcte