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Dirac's hole theory versus quantum field theory
Dirac's hole theory and quantum field theory are usually considered
equivalent to each other. For models of a certain type, however, the
equivalence may not hold as we discuss in this Letter. This problem is closely
related to the validity of the Pauli principle in intermediate states of
perturbation theory.Comment: No figure
Top quark forward-backward asymmetry from the model
The forward-backward asymmetry in top quark pair production,
measured at the Tevatron, is probably related to the contribution of new
particles. The Tevatron result is more than a deviation from the
standard model prediction and motivates the application of alternative models
introducing new states.
However, as the standard model predictions for the total cross section
and invariant mass distribution for this process are in
good agreement with experiments, any alternative model must reproduce these
predictions. These models can be placed into two categories: One introduces the
s-channel exchange of new vector bosons with chiral couplings to the light
quarks and to the top quark and another relies on the t-channel exchange of
particles with large flavor-violating couplings in the quark sector. In this
work we employ a model which introduces both s- and t-channel nonstandard
contributions for the top quark pair production in proton antiproton
collisions. We use the minimal version of the model (3-3-1 model) that predicts the existence of a new neutral gauge
boson, called . This gauge boson has both flavor-changing couplings
to up and top quarks and chiral coupling to the light quarks and to the top
quark. This very peculiar model coupling can correct the for top quark
pair production for two ranges of mass while leading to cross
section and invariant mass distribution quite similar to the standard model
ones. This result reinforces the role of the 3-3-1 model for any new physics
effect.Comment: 12 pages, 4 figures, 2 table
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