Top quark production at future lepton colliders in the asymptotic regime

Abstract

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 allows to derive the leading asymptotic terms of various observables using the same theoretical description that was used for light quark production. Explicit examples are shown for the Standard Model and the Minimal Supersymmetric Standard Model cases.Comment: 20 pages and 13 figures. e-mail: renard@lpm.univ-montp2.f

Split supersymmetry at the logarithmic test of future colliders

“…[9,11], because of a typical gauge cancellation between splitting and parameter renormalization, the contributions to the single log cancels, and it remains only the quadratic log contribution feeded by the three gauge boson coupling, which is a pure SM term. So, owing to this cancellation, the universal coefficient is the same in all cases (SM, Split, "m.l.…”

“…For what concerns the notations and the conventions, we shall follow the same ones as in Ref. [7][8][9]. To make, though, this Section more easily and quickly readable by a reader who were not too interested in the technical details, we have devoted a final Appendix to the complete definition of the several terms that appear in our formulae.…”

“…After this long but, we hope, useful preliminary discussion, we are now ready to list the Sudakov expansion for Split Supersymmetry for a number of processes, starting with those that have been previously mentioned. To these expansions we shall add (and list) the corresponding ones that were obtained [7][8][9] in the case of "moderately light" Supersymmetry, essentially to evidentiate the big numerical difference between the effects in the two cases. We shall define in this paper this second scenario as "moderately light MSSM" and indicate it with the shorthand notation "m.l.…”

“…[9,7] and for each type of term we indicate the modification arising when passing from the MSSM case with a light SUSY scale to the Split case with heavy scalars.…”

Processese−e+→γγ,Zγ,ZZin the standard

“…In terms of the invariant amplitudes defined in (A.4), they are written as 9) and for all processes it is found that N Born, t 3,9 = N Born, u…”