0000000000853622
AUTHOR
T. G. Steele
The Nielsen identities for the two-point functions of QED and QCD
We consider the Nielsen identities for the two-point functions of full QCD and QED in the class of Lorentz gauges. For pedagogical reasons the identities are first derived in QED to demonstrate the gauge independence of the photon self-energy, and of the electron mass shell. In QCD we derive the general identity and hence the identities for the quark, gluon and ghost propagators. The explicit contributions to the gluon and ghost identities are calculated to one-loop order, and then we show that the quark identity requires that in on-shell schemes the quark mass renormalisation must be gauge independent. Furthermore, we obtain formal solutions for the gluon self-energy and ghost propagator i…
Improved determination of the mass of the1−+light hybrid meson from QCD sum rules
We calculate the next-to-leading order (NLO) ${\ensuremath{\alpha}}_{s}$ corrections to the contributions of the condensates $〈\ensuremath{\alpha}{G}^{2}〉$ and $〈\overline{q}q{〉}^{2}$ in the current-current correlator of the hybrid current $g\overline{q}(x){\ensuremath{\gamma}}_{\ensuremath{\nu}}{\mathrm{iF}}_{\ensuremath{\mu}\ensuremath{\nu}}^{a}{T}^{a}q(x)$ using the external field method in the Feynman gauge. After incorporating these NLO contributions into the Laplace sum rules, the mass of the ${J}^{\mathrm{PC}}{=1}^{\ensuremath{-}+}$ light hybrid meson is recalculated using the QCD sum rule approach. We find that the sum rules exhibit enhanced stability when the NLO ${\ensuremath{\alp…