Closed String Radiation from the Interaction of the Moving D$p$-branes with Background Fields

At first, we derive a boundary state, associated with a moving D$p$-brane, in the presence of the Kalb-Ramond field and a $U(1)$ gauge potential. Then, from the interaction of such D$p$-branes, we obtain the radiation amplitude for a massless closed string. The behavior of the radiation amplitude for the large distance of the branes will be studied. Our calculations is in the framework of the bosonic string theory.