  We study the narrow decay width of low-lying penta-quark baryons in the QCD
string theoryin terms of gluonic excitations. In the QCD string theory, the
penta-quark baryon decays via a gluonic-excited state of a baryon and meson
system, where a pair of Y-shaped junction and anti-junction is created. Since
lattice QCD shows that the lowest gluonic-excitation energy takes a large value
of about 1 GeV, the decay of the penta-quark baryon near the threshold is
considered as a quantum tunneling process via a highly-excited state (a
gluonic-excited state) in the QCD string theory. This mechanism strongly
suppresses the decay and leads to an extremely narrow decay width of the
penta-quark system.
