Photoproduction of possible pentaquark states ${\Lambda }_b^0(5912)$ and ${\Lambda }_b^0(5920)$ in the $\gamma p\to {\Lambda }_b^{0(\ast )}{B}^{+}$ reactions

Abstract

In this work, we report on a theoretical study of possible pentaquark states ${\Lambda }_b^0(5912)$ and ${\Lambda }_b^0(5920)$ in the $\gamma p\to {\Lambda }_b^{0(\ast )}{B}^{+}$ reactions within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole and $t$-channel ${\bar{B}}^{\ast -}$ exchange, the contact term contribution are also included. Our theoretical approach is based on the chiral unitary theory where the ${\Lambda }_b^0(5912)$ and ${\Lambda }_b^0(5920)$ resonances are dynamically generated. Within the coupling constants of the ${\Lambda }_b^0(5912)$ and ${\Lambda }_b^0(5920)$ to $\bar{B}p$ and ${\bar{B}}^{\ast }p$ channels obtained from chiral unitary theory, the total and differential cross sections of the $\gamma p\to {\Lambda }_b^{0(\ast )}{B}^{+}$ are evaluated. Our calculation indicates that the cross section for $\gamma p\to {\Lambda }_b^0(5912)B^{+}$ and $\gamma p\to {\Lambda }_b^0(5920)B^{+}$ reactions are of the order of 0.0164 nb and 0.00527 nb,respectively. If measured in future experiments, such as Electron-Ion Collider in China (EicC) or US(US-EIC), the predicted total cross sections and specific features of the angular distributions can be used to test the (molecular) nature of the ${\Lambda }_b^0(5912)$ and ${\Lambda }_b^0(5920)$ that they may be pentaquark states.