Magnetic moment of the pentaquark Theta^+(1540) as diquark-diquark-antiquark state with QCD sum rules

In this article, we study the magnetic moment of the pentaquark state $ \Theta^+(1540)$ as diquark-diquark-antiquark ($[ud][ud]\bar{s}$) state with the QCD sum rules in the external weak electromagnetic field (EFSR) and the light-cone QCD sum rules (LCSR) respectively. The numerical results indicate the magnetic moment is about $\mu_{\Theta^+}=-(0.11\pm 0.02)\mu_N$ for the EFSR and $\mu_{\Theta^+}\approx-(0.1-0.5)\mu_N$ for the LCSR. As the values obtained from the EFSR are more stable than the corresponding ones from the LCSR, $\mu_{\Theta^+}=-(0.11\pm 0.02)\mu_N$ is more reliable.