6 research outputs found
Nucleon Helicity in Pion Photoproduction
Pion-photoproduction data is examined to check for the nucleon-helicity
conservation predicted by asymptotic QCD. The differential cross section shows
agreement with constituent-counting rules, and polarization data is not in
disagreement with conservation of nucleon helicity. However large uncertainties
in the polarization measurements do not allow a conclusive statement. The
helicity amplitudes from a partial-wave analysis are also examined for helicity
conservation. While the amplitudes become small as increases, the
dependence of the helicity-conserving amplitudes is similar to the dependence
of the non-conserving amplitudes.Comment: plain tex, 6 pages, 8 figure
Monopole Condensation and Dimensional Transmutation in SU(2) QCD
We resolve the controversy on the stability of the monopole condensation in
the one-loop effective action of SU(2) QCD by calculating the imaginary part of
the effective action with two different methods at one-loop order. Our result
confirms that the effective action for the magnetic background has no imaginary
part but the one for the electric background has a negative imaginary part.
This assures that the monopole condensation is indeed stable, but the electric
background becomes unstable due to the pair-annihilation of gluons.Comment: 13 pages, 2 figure