Related papers: Fermion pair production at LEP2 and interpretation…
A complete discussion of the constraints on the Michel parameters and the ambiguities of their interpretation is presented. Estimators of new physics, optimized for a very wide class of hypotheses and models, are proposed.
The production of four fermions plus a visible photon in electron-positron collisions is analyzed, with particular emphasis on the LEP2 energy range. The study is based on the calculation of exact matrix elements, including the effect of…
We present a comprehensive study of pair production and decay of stops, sbottoms, and staus in $e^+ e^-$ annihilation at LEP2. We give numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay…
Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects…
The measurements of four-fermion production rates performed at LEP2 in e+e- collisions at centre-of-mass energies ranging from 161 to 209 GeV are presented. The focus is put on processes that involve the production and decay of W or Z…
We investigate the effects of R-parity-violating $LL\bar E$ and $LQ\bar D$ operators on the production of fermion pairs at a $\mu^+ \mu^-$ collider with high energy and luminosity. We show that comparison of angular distributions leads to…
We quantitatively discuss the possibility of deriving model-independent constraints on the general four-fermion contact interaction couplings, from the currently available data on the two-fermion production processes $e^+e^-\to\mu^+\mu^-$,…
A data sample corresponding to an integrated luminosity of 232pb^-1 was collected in 1997 and 1998 by the L3 experiment at LEP in e+e- collisions at centre-of-mass energies between 181.7GeV and 188.7GeV. Pair production of fermions and…
Events stemming from the pair-production of Z bosons in e^+e^- collisions are studied using 217.4 pb^-1 of data collected with the L3 detector at centre-of-mass energies from 200 GeV up to 209 GeV. The special case of events with b quarks…
A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about…
In five years of operation (1996-2000) the four LEP2 experiments collected roughly 3 fb-1 of data from e+e- collisions at centre-of-mass energies between 161 and 207 GeV, yielding a total of about 40000 W-pair events. The analysis of the…
The production of a tt(bar) pair from lepton-antilepton annihilation is considered for values of the center of mass energy much larger than the top mass, typically of the few TeV size. In this regime a number of simplifications occurs that…
We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present data still allow for the presence of a new quark and/or lepton doublet with masses greater than $M_Z/2$,…
This talk is divided in two parts. In the first one we discuss the signals of the Minimal Supersymmetric Standard Model through the production of \tilde{e} \tilde{q}. The second part is devoted to contact terms. The bounds on the mass scale…
We compute fermion pair production cross sections in $e^+e^-$ annihilation in models of electroweak symmetry breaking in warped 5-dimensional space. Our analysis is based on a framework with no elementary scalars, only gauge bosons and…
The LEP data on four fermion processes are presently used to study the non abelian gauge couplings of the Standard Model. The present theoretical error for two classes of processes, single-W production and radiative four fermion final…
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…
A summary is given on the experimental bounds for the couplings and masses of scalar and vector leptoquarks associated to the first fermion generation. We investigate to which extent an interpretation of the recently reported excess of…
We study the Higgs pair-production in the Standard Model of the strong and electroweak interactions at future $e^{+}e^{-}$ collider energies, with the reaction $e^{+}e^{-}\to t \bar t HH$. We evaluated the total cross section of $t\bar tHH$…
We analyze the manifestations of new matter particles predicted by models of new physics beyond the Standard Model, at present and future high--energy colliders. We consider both the production of these new particles and some of their…