Density dependent relativistic hadron theory for hadron matter with inclusion of pentaquark $\Theta^+$

Abstract

The density dependent relativistic hadron field theory(DDRH) is extended to inclusions of pentaquark $\Theta^+$. We investigate In-medium properties of $\Theta^+$ and nucleons. As well as the neutron and proton,the effective $\Theta^+$ mass decreases as the baryon density increases,and remains larger than nucleons'. The effective mass of $\Theta^+$ is calculated,$M^*_{\Theta^+}\simeq0.71M_{\Theta^+}$ at normal nuclear density with the fraction of $\Theta^+$ 0.2. The effective masses of all baryon increase with the increasing fraction of $\Theta^+$. The binding energy is also studied. We find the binding energy is much larger than it in nuclear matter without $\Theta^+$,and then discuss the stability of the system with conclusions of pentaquark $\Theta^+$. It is shown that the system becomes bounder added small fraction of $\Theta^+$. Finally we discuss the condition when the system is the most stable and calculate the minimum of binding energy and the fractions of all baryons as functions of baryon density.