Systematic study on production of hidden-bottom pentaquark via $\gamma p$ and ${\pi }^{-}p$ scatterings

Abstract

The production of hidden-bottom pentaquark $P_b$ states via $\gamma p$ and ${\pi }^{-}p$ scatterings is studied within an effective Lagrangian approach and the vector-meson-dominance mechnism. For the $P_b$ production in the process $\gamma p\to {\rm Y}p$, the dipole Pomeron model is employed to calculate the background contribution, and the experimental data can be well described. For the process ${\pi }^{-}p\to {\rm Y}n$, the Reggeized $t$-channel with $\pi$ exchange is considered as the main background for the $P_b$ production. Near the threshold, two-peak structure from the states P_{b (11080) and $P_b(11125)$ can be observed if energy bin width is chosen as 0.01 GeV, and the same result is obtained in the ${\pi }^{-}p$ scattering. Moreover, by taking the branching ratio of Br$[P_b\to \pi N]\simeq 0.05\%$, the numerical result shows that the average value of cross section from the $P_b(11080)$ state produced in the $\gamma p$ or ${\pi }^{-}p$ scattering reaches at least 0.1 nb with a bin of 0.1 GeV. Even if we reduce the branching ratio of the $P_b$ state into $\pi N$ channel by one order, the theoretical average of the cross section from $P_b(11080)$ production in ${\pi }^{-}p$ scattering can reach the order of 0.01 nb with a bin of 0.1 GeV, which means that the signal can still be clearly distinguished from the background. The experimental measurements and studies on the hidden-bottom pentaquark $P_b$ state production in the $\gamma p$ or ${\pi }^{-}p$ scattering near-threshold energy region around $W\simeq 11$ GeV are strongly suggested, which are accessible at COMPASS and JPARC. Particularly, the result of the photoproduction suggests that it is very promising to observe the hidden-bottom pentaquark at proposed EicC facility in China.

Comments: 7 pages, 7 figures