Double Chargino Production in e−e−e^{-}e^{-} scattering

We point out the production of the charginos and neutralinos in electron-electron process in several supersymmetric models, in order to show that the International Linear Collider can discover double charged charginos if these particles really exist in nature.Comment: 9 pages, 9 figures, Talk given at CTP symposium on Supersymmetry at LHC: Theoretical and Experimental Perspectives, The British University in Egypt, Cairo, Egypt, 11-14 March 200

Fermion and Sfermion Effects in e+e−e^+ e^- charged Higgs pair production

Top and bottom one loop corrections to $e^+e^-\rightarrow H^+ H^-$ are considered at NLC energies and found to be significantly large and negative over the full range of $tan \, \beta$. Moreover, loop effects of moderately heavy squarks and sleptons in the minimal supersymmetric extension of the standard model, tend to cancel partly or fully these large corrections, thus providing a useful indirect information about the supersymmetric sector. The overall effect can still range between $-25 \%$ and $+25 \%$, however lies typically around $-10 \%$ in a wide range of the model parameters.Comment: latex, 16 pages and 9 figures (appended as a postscript file) SLAC--PUB--6529, PM/94-1

The Other Natural Two Higgs Doublet Model

We characterize models where electroweak symmetry breaking is driven by two light Higgs doublets arising as pseudo-Nambu-Goldstone bosons of new dynamics above the weak scale. They represent the simplest natural two Higgs doublet alternative to supersymmetry. We construct their low-energy effective Lagrangian making only few specific assumptions about the strong sector. These concern their global symmetries, their patterns of spontaneous breaking and the sources of explicit breaking. In particular we assume that all the explicit breaking is associated with the couplings of the strong sector to the Standard Model fields, that is gauge and (proto)-Yukawa interactions. Under those assumptions the scalar potential is determined at lowest order by very few free parameters associated to the top sector. Another crucial property of our scenarios is the presence of a discrete symmetry, in addition to custodial SO(4), that controls the $T$-parameter. That can either be simple CP or a $Z_2$ that distinguishes the two Higgs doublets. Among various possibilities we study in detail models based on SO(6)/SO(4)$\times$ SO(2), focussing on their predictions for the structure of the scalar spectrum and the deviations of their couplings from those of a generic renormalizable two Higgs doublet model.Comment: 54 page

An effective lagrangian description of charged Higgs decays H^+ -> Wg, WZ and Wh

Charged Higgs decays are discussed within an effective lagrangian extension of the two-higgs doublet model, assuming new physics appearing in the Higgs sector of this model. Low energy constrains are used to imposse bounds on certain dimension -six operators that describe the modified charged Higgs interactions. These bounds are used then to study the decays H^+ -> Wg, WZ and Wh, which can have branching ratios of order 10^-5, 10^-1 and O(1), respectively; thse modes are thus sensitive probes of the symmetries of the Higgs sector that could be tested at future colliders.Comment: 15 pages, 3 figure

Electroweak radiative corrections to the three channels of the process f_1 bar-f_1 ZA --> 0

We have calculated the electroweak radiative corrections at the O(alpha) level to the three channels of the process f_1 bar-f_1 Z A --> 0 and implemented them into the SANC system. Here A stands for the photon and f_1 for a first generation fermion whose mass is neglected everywhere except in arguments of logarithmic functions. The symbol --> 0 means that 4-momenta of all the external particles flow inwards. We present the complete analytical results for the covariant and helicity amplitudes for three cross channels: f_1 + bar-f_1 --> Z + gamma, Z --> f_1 + bar-f_1 + gamma and f_1 + gamma --> f_1 + Z. The one-loop scalar form factors of these channels are simply related by an appropriate permutation of their arguments s,t,u. To check the correctness of our results we first of all observe the independence of the scalar form factors on the gauge parameters and the validity of the Ward identity, i.e. external photon transversality, and, secondly, compare our numerical results with the other independent calculations available to us.Comment: 19 pages, 6 figures, 10 table

Lepton masses in a supersymmetric 3-3-1 model

We consider the mass generation for both charginos and neutralinos in a 3-3-1 supersymmetric model. We show that R-parity breaking interactions leave the electron and one of the neutrinos massless at the tree level. However the same interactions induce masses for these particles at the 1-loop level. Unlike the similar situation in the MSSM the masses of the neutralinos are related to the masses of the charginos.Comment: RevTex, 11 pages incluing 2 .eps figures. Extended published versio

QCD corrections to scalar quark pair production in e+e- annihilation

We calculate the QCD radiative corrections to the production of supersymmetric scalar partners of quarks in e+e- annihilation. We include both the standard gluonic corrections and the genuine supersymmetric QCD corrections due to quark--gluino loops, and allow for mixing between left-- and right--handed scalar quarks which leads to the possibility that the two final state particles have different masses. The corrections are found to be much larger than the ones affecting the production of spin 1/2 particles.Comment: one typo corrected (2d paragraph of setion 5) and a better set of figures has been included as an uuencoded compressed tar postscript fil

Weak radiative corrections at LEP

Weak radiative corrections in the Weinberg-Salam model are reviewed, in the perspective of new results at LEP. They should be identified with good precision. This would settle Weinberg-Salam model position among various possible extensions