Light scalar top quark ate+e−colliders

Abstract

We examine the production and decay of a supersymmetric scalar top i t at e 'e colliders such as TRISTAN at KEK, the Stanford Linear Collider, and LEP at CERN, based on supersymmetric models with soft breaking. Existing bounds for supersymmetric particles imply that T I in the energy range of these colliders would be lighter than other scalar quarks and than the top quark. We make a careful study of available TI decay modes in this scenario. The flavor-changing decay il -cp is found to proceed through the misalignment of the scalar-quark and quark mixing matrices. If the three-body decay i; +bl+? is kinematically accessible it dominates the two-body decay. The decay Tl-bv7+ is even larger due to different chirality structure, but is likely to suffer from a large phasespace suppression. Four-body decays are negligible. The & pair production cross section including the y and Z contribution and the left-right mixing is presented.

Light stop searches at the LHC in events with one hard photon or jet and missing energy

“…For this work, it is assumed that the two-body decayt 1 → c +χ 0 1 is enhanced by large logarithms from renormalization group evolution [8,21] so that this decay channel becomes dominant and the stop decay length is too short to be observable. Alternative scenarios where the partial width fort 1 → cχ 0 1 is small lead to interesting signals from the competing four-body decayt 1 → b l + ν lχ 0 1 and displaced stop decays [21] but will not be investigated further here.…”

“…Acceptable values of the relic density for heavy CP-odd Higgs bosons are naturally obtained in the stop-neutralino co-annihilation region, in which the neutralino-stop mass difference is of about a few tens of GeV [5]. In this case, the three-body stop decay channel into W boson, bottom quark and the lightest neutralino is kinematically closed, and the loop-induced two-body decay into a charm and a neutralino tends to be the dominant stop decay mode [8]. Searches for a stop decaying into a charm plus missing energy at the Tevatron collider rely on a sufficiently energetic charm quark, in order to trigger on these events.…”

Diffractive supersymmetric particle production at the CERN LHC

“…bH ~0 1 are kinematically not accessible, the main decay mode is expected to be the loop-induced flavor-violating decayt 1 ! c~0 1 [54]. The decay width of the lightest top squark is then given by [54]:…”

Searches for sleptons and squarks in e+e− collisions at 189 GeV

“…The stop can decay ast → cχ or t → b ν [2]. The first decay can proceed only via loop diagrams and thus has a very small width, of the order of 0.01-1 eV [2]. Thet → b ν channel proceeds via virtual chargino exchange and has a width of the order of 0.1-10 keV [2].…”

“…The stop can decay ast → cχ or t → b ν [2]. The first decay can proceed only via loop diagrams and thus has a very small width, of the order of 0.01-1 eV [2].…”