20 research outputs found
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A GAUGE-INVARIANT MULTIPOLE EXPANSION SCHEME FOR HEAVY-QUARK SYSTEMS IN QUANTUM CHROMODYNAMICS
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SOFT-GLUON DYNAMICS FOR HEAVY QUARK-ANTIQUARK SYSTEMS
The interaction of a heavy quark-antiquark system with color gluons is classified according to the gluon energy, and a manifestly gauge-invariant multipole expansion scheme is constructed. This multipole expansion has useful applications to the study of hadronic transitions between heavy-quark-antiquark bound states, the static quark-antiquark potential and the nonperturbative structure of the gluonic vacuum
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SOFT-GLUON EFFECTS IN NONLEPTONIC DECAYS OF CHARMED MESONS
Soft-gluon effects in nonleptonic decays of D and F mesons are studied nonperturbatively by use of a QCD multipole expansion. For reasonable values of D-meson bound-state parameters, the soft-gluon effects lead to a significant difference in the lifetimes of the D{sup 0} and D{sup +} mesons
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SOFT-GLUON EFFECTS IN CHARMED-MESON DECAYS
In D/sup 0/- and F/sup +/-meson decays, QCD effects are expected to activate W-exchange processes (quark-annihilation processes), as shown in Figs. 2 and 3, which by themselves are strongly suppressed because of helicity mismatch. For example, the D/sup 0/ meson, on gluon emission, can flip its spin so that the subsequent weak decay proceeds without helicity suppression. Hard-gluon emission from the D/sup 0/ meson, evaluated perturbatively, enhances the D/sup 0/ decay rate (by approx. 20%). Soft-gluon emission is an equally likely source of enhancements in charmed-meson decays, and indeed seems to be the dominant one. This soft-gluon effect in charmed-meson decays was studied by a nonperturbative method that has theoretical foundations in QCD. The basic tool is a multipole expansion in QCD. The analysis is divided into three steps: virtual color-fluctuation of charmed mesons, separation of long-distance and short-distance phenomena by use of QCD multipole expansion, and evaluation of the soft-gluon effect
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A GAUGE-INVARIANT MULTIPOLE EXPANSION SCHEME FOR HEAVY-QUARK SYSTEMS IN QUANTUM CHROMODYNAMICS
Separation of short-distance and long-distance dynamics for heavy quark-antiquark systems interacting with color gluons is investigated through a classification of gluons according to their ranges. A gauge-invariant double-multipole expansion scheme is constructed which takes into account color fluctuation of heavy-quark systems. Hadronic transitions between heavy quark-antiquark bound states as well as the static quark-antiquark potential are studied within this framework