Masses and Magnetic Moments of Doubly Heavy Tetraquarks via Diffusion Monte Carlo Method

We present mass spectrum and magnetic moments of the $\bar{n}\bar{n}QQ$ states, where $n=u,d,s$ and $Q=c,b$. We solve four-body Schr\"odinger equation with a quark potential model by using diffusion Monte Carlo (DMC) method. The quark potential is based on the Coulomb, confinement and spin-spin interaction terms. We find mass and magnetic moment of the $T_{cc}^+$ state as $M_{T_{cc}^+}=3892 ~\text{MeV}$ and $\mu=0.28 \mu_N$, respectively. We also find the mass and magnetic moment of $T_{bb}^-$ as $M_{T_{bb}^-}=10338 ~\text{MeV}$ and $\mu=-0.32 \mu_N$, respectively. We find some bound state candidates of doubly heavy tetraquark systems with $I(J^P)=0(1)^+$ $nn \bar b \bar b$, $I(J^P)=0(0)^+$ $nn \bar c \bar b$, $I(J^P)=0(1)^+$ $nn \bar c \bar b$, and $I(J^P)=1/2(1)^+$ $ns \bar b \bar b$. We compare our results with other approaches in the literature.