The width of ${\Theta }^{+}$ for large $N_c$ in chiral quark soliton model

Abstract

In the chiral quark soliton model the smallness of ${\Theta }^{+}$ width is due to the cancellation of the coupling constants which are of different order in $N_c$. We show that taking properly into account the flavor structure of relevant SU(3) representations for arbitrary number of colors enahnces the nonleading term by an additional factor of $N_c$, making the cancellation consistent with the $N_c$ counting. Moreover, we show that, for the same reason, ${\Theta }^{+}$ width is suppressed by a group-theoretical factor $\mathcal{O}(1/N_c)$ with respect to $\Delta$ and discuss the $N_c$ dependence of the phase space factors for these two decays.

Comments: 9 pages, 3 eps figures, in v2 reference added, minor typos corrected