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]

Remarkable virtual SUSY effects in W±W^{\pm} production at high energy hadron colliders

We present a complete 1-loop study of the electroweak corrections to the process $ug\to dW^+$ in MSSM and SM. The occurrence of a number of remarkable properties in the behavior of the helicity amplitudes at high energies is stressed, and the crucial role of the virtual SUSY contributions in establishing them, is emphasized. The approach to asymptopia of these amplitudes is discussed, comparing the effects of the logarithmic and constant contributions to the mass suppressed ones, which are relevant at lower energies. Applying crossing to $ug\to d W^+$, we obtain all subprocesses needed for the 1-loop electroweak corrections to $W^\pm$-production at LHC. The SUSY model dependence of such a production is then studied, and illustrations are given for the transverse $W^{\pm}$ momentum distribution, as well as the angular distribution in the subprocess center of mass.Comment: 21 pages, 12 figures, version to appear in Phys.Rev.

Remarkable virtual SUSY effects in W±W^{\pm} production at high energy hadron colliders

We present a complete 1-loop study of the electroweak corrections to the process $ug\to dW^+$ in MSSM and SM. The occurrence of a number of remarkable properties in the behavior of the helicity amplitudes at high energies is stressed, and the crucial role of the virtual SUSY contributions in establishing them, is emphasized. The approach to asymptopia of these amplitudes is discussed, comparing the effects of the logarithmic and constant contributions to the mass suppressed ones, which are relevant at lower energies. Applying crossing to $ug\to d W^+$, we obtain all subprocesses needed for the 1-loop electroweak corrections to $W^\pm$-production at LHC. The SUSY model dependence of such a production is then studied, and illustrations are given for the transverse $W^{\pm}$ momentum distribution, as well as the angular distribution in the subprocess center of mass.Comment: 21 pages, 12 figures, version to appear in Phys.Rev.

Subleading terms in asymptotic Passarino-Veltman functions

We write explicit and self-contained asymptotic expressions for the tensorial B, C and D Passarino-Veltman functions. These include quadratic and linear logarithmic terms, as well as subleading constant terms. Only mass-suppressed O(m^2/s) contributions are neglected. We discuss the usefulness of such expressions, particularly for studying one-loop effects in 2-to-2 body processes at high energy.Comment: 25 pages, 9 eps figure

The gamma gamma to Z Z process and the search for virtual SUSY effects at a gamma gamma Collider

We study the helicity amplitudes of the process gamma gamma to ZZ in the Standard Model at high energy. These amplitudes receive contributions from the W and charged quark and lepton loops, analogous to those encountered in the gamma gamma to gamma gamma, gamma Z cases studied before. But gamma gamma to ZZ also receives contributions from the Higgs s-channel poles involving the effective Higgs-gamma gamma vertex. At energies of about 300 GeV, the amplitudes in all three processes are mainly helicity-conserving and almost purely imaginary; which renders them a very useful tool in searching for New Physics. As an example, a SUSY case is studied, and the signatures due to the virtual effects induced by a chargino-, charged slepton- or a lightest stop-loop in gamma gamma to ZZ, are explored. These signatures, combined with the analogous ones in gamma gamma to gamma gamma and gamma gamma to gamma Z, should help identifying the nature of possible New Physics particles.Comment: 28 pages and 6 figures; version to appear in E.P.J.C e-mail: [email protected]