Nonstandard top substructure

Probing nonstandard top-quark couplings using spin correlation

Top spin correlation has been shown to be nontrivial in hadronic top-quark pair production, and can be realized by the asymmetries of the decay products of the top quark and antiquark. We show in this work that the top spin correlation is a sensitive probe to the anomalous top-quark couplings beyond the standard model. Specifically, we look at the anomalous chromomagnetic and chromoelectric dip...

Limits on nonstandard top quark couplings from electroweak measurements.

We calculate the typical size of loop corrections to electroweak observables arising from non-standard Ztt and Wtb vertices. We use an effective Lagrangian formalism based on the electroweak gauge group SU(2)L× U(1)Y → U(1)EM . Limits on the non-standard model top quark couplings from electroweak observables are presented and compared with previously obtained limits. ∗This manuscript has been a...

Phenomenology of a nonstandard top quark Yukawa coupling.

There are theoretical speculations that the top quark may have different properties from that predicted by the standard model. We use an effective Lagrangian technique to model such a non-standard top quark scenario. We parametrize the CP violating interactions of the top quark with the bubble wall in terms of an effective top quark Yukawa coupling, then study its effects on the electroweak bar...

Top production at the Tevatron/LHC and nonstandard, strongly interacting spin one particles

In this note, we consider possible constraints from tt̄ production on the gauge bosons of theories with an extended strong interaction sector such as axigluons or flavour universal colorons. Such constraints are found to be competitive with those obtained from the dijet data. The current tt̄ data from the Tevatron rule out axigluon masses (mA) up to 900 GeV and 850 GeV at 2 σ and 4 σ levels respe...

FOUNDATIONS OF NONSTANDARD ANALYSIS A Gentle Introduction to Nonstandard Extensions