We consider the flavor changing neutral current(FCNC) process e + e − →tc(or tc) in the context of topcolor-assisted technicolor(TC2) models. We find that the contributions of charged scalars (technipions and top-pions) and topcolor gauge bosons are negligibly small. The neutral scalars (top-pion π 0 t and top-Higgs h 0 t ) can give significant contributions to this process. With reasonable values of the parameters in TC2 models, there will be several tens of the observabletc events to be generated in the future e + e − linear colliders.
Results are presented on a measurement of the t t pair production cross section in pp collisions at ͱs ϭ1.8 TeV from nine independent decay channels. The data were collected by the DØ experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events is observed with an expected background of 38.8Ϯ3.3 events. For a top quark mass of 172.1 GeV/c 2 , the measured cross section is 5.69 Ϯ1.21(stat)Ϯ1.04(syst) pb.
In the framework of topcolor-assisted technicolor(TC2) models, we calculate the contributions of flavor changing scalar couplings involved the neutral top-pion π 0 t and top-Higgs h 0 t to the branching ratio B r (t −→ cg). We find that the value of B r (t −→ cg) can reach 1 × 10 −3 with reasonable values of the parameters in TC2 models, which may be testable in the future experiments.
We study the production and decay of the neutral top-pion π 0 t predicted by topcolor-assisted technicolor(TC2) theory. Our results show that, except the dominant decay modes bb,tc and gg, the π 0 t can also decay into γγ and Zγ modes. It can be significantly produced at high energy e + e − collider(LC) experiments via the processes e + e − → π 0 t γ and e + e − → Zπ 0 t . We further calculate the production cross sections of the processes e + e − → γπ 0 t → γtc and e + e − → Zπ 0 t → Ztc. We find that the signatures of the neutral top-pion π 0 t can be detected via these processes.PACS number(s): 12.60Nz, 14.80.Mz
We study the contributions of the technipion P0 predicted by the
technicolour theory to the process e+e-→Zbb̄. Our
results show that the production cross section σ is very small.
The value of the cross section σ is smaller than
3×10-3 fb for most technicolour models. It is
impossible for the recent experimental results at LEPII
to be explained within the framework of technicolour
theory.
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