Blowup dynamics for mass critical Half-wave equation in 2D

We consider the half-wave equation $i{u}_t=Du-\mathrm{\mid }u\mathrm{\mid }u$ in two dimensions. For the initial data $u_0(x)\in H^s({\mathbb{R}}^2)$, $s\in (\frac{3}{4},1)$, we obtain the non-radial ground state mass blow-up solutions with the blow-up speed $\mathrm{\parallel }{D}^{\frac{1}{2}}u(t){\mathrm{\parallel }}_{L^2}\sim \frac{1}{\mathrm{\mid }t\mathrm{\mid }}$ as $t\to 0^{-}$.