Abstract
The basic structure of top-quarks as spin-1/2 particles is characterized by the radius Rt and the intrinsic magnetic dipole moment κt, both individually associated with gauge interactions. They are predicted to be zero in pointlike theories as the Standard Model. We derive upper limits of these parameters in the color sector from cross sections measured at Tevatron and LHC in top pair production pp¯/pp→tt¯, and we predict improved limits expected from LHC in the future, especially for analyses exploiting boosted top final states. An additional method for measuring the intrinsic parameters is based on tt¯+jet final states.
Highlights
The basic structure of top-quarks as spin-1/2 particles is characterized by the radius Rt and the intrinsic magnetic dipole moment κt, both individually associated with gauge interactions
We derive upper limits of these parameters in the color sector from cross sections measured at Tevatron and LHC in top pair production p p /pp → tt, and we predict improved limits expected from LHC in the future, especially for analyses exploiting boosted top final states
The top-quark is the heaviest particle in the Standard Model (SM), even if the Higgs particle is included as a contender
Summary
The top-quark is the heaviest particle in the Standard Model (SM), even if the Higgs particle is included as a contender. The top-quark may be endowed with intrinsic structure at the TeV scale This should be contrasted with the pointlike character of all fundamental fields within the Standard Model, extending up to scales close to the Planck scale for low Higgs mass. Assuming Λ∗ to be of order 1 TeV and beyond, compatible with bounds on contact interactions from Tevatron and LHC [12], κt could be expected at the level of several per-cent Both the anomalous parameters, color radius and color magnetic dipole moment, can be introduced through effective Lagrangians [13] in an SU(3)c gauge-invariant and parity-even form: LR. The events of the ttq process, characterized by a forward moving t-quark plus a tq-pair, with the two partons in the pair balanced in transverse momentum, signal Rutherford qt scattering. [Elastic gluon-top scattering is independent of the radius Rt and cannot be exploited.]
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