Decay width of the pentaquark state ${\Theta }^{+}(1540)$ with QCD sum rules

In this article, we take the point of view that the pentaquark state ${\Theta }^{+}(1540)$ has negative parity, and choose the diquark-triquark type interpolating current to calculate the strong coupling constant $g_{\Theta NK}$ in the QCD sum rules approach. Our numerical results indicate the values of the strong coupling constant $g_{\Theta NK}$ are very small, $|g_{\Theta NK}|=0.175\pm 0.084$, and the width is ${\Gamma }_{\Theta }<4\mathrm{MeV}$, which can explain the narrow width $\Gamma \le 10\mathrm{MeV}$ naturally.

Figure 1

$|g_{\Theta NK}|$ with $M_1^2$ for $M_2^2=1.3{\mathrm{GeV}}^2$, $t_0=0.9{\mathrm{GeV}}^2$.

Figure 2

$|g_{\Theta NK}|$ with $M_2^2$ for $M_1^2=1.7{\mathrm{GeV}}^2$, $s_0=1.9{\mathrm{GeV}}^v$.