Black Hole from Black Hole in Two Dimensions

We present a new class of quantum two dimensional dilaton gravity model, which is described by $SL(2,R)/U(1)$ gauged Wess-Zumino-Witten model deformed by $(1,1)$-operator. We analyze the model by ${1 \over k}$ expansion ($k$ is the level of $SL(2,R)$ Wess-Zumino-Witten model) and we find that the curvature singularity does not appear when $k$ is large and the Bondi mass is bounded from below. Furthermore, the rate of the Hawking radiation in the quantum black hole created by shock wave goes to zero asymptotically and the radiation stops when the Bondi mass vanishes.