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 $\gamma p\rightarrow \Upsilon p$, the dipole Pomeron model is employed to calculate the background contribution, and the experimental data can be well described. For the process $\pi ^{-}p\rightarrow \Upsilon n$, 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$[{P_{b}\rightarrow \pi N}]\simeq 0.05\%$, 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.
Highlights
Three narrow hidden-charm pentaquark states, Pcð4312Þ; Pcð4440Þ, and Pcð4457Þ, were observed by the LHCb Collaboration [1]
Even if we reduce the branching ratio of the Pb state into πN channel by one order, the theoretical average of the cross section from Pbð11080Þ production in π−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
It is found that the contribution from pentaquark Pb state shows a very sharp peak near the threshold, and the experimental point at high energy is well consistent with the cross section of the Pomeron diffractive process
Summary
Three narrow hidden-charm pentaquark states, Pcð4312Þ; Pcð4440Þ, and Pcð4457Þ, were observed by the LHCb Collaboration [1]. In the current work, we will study the possibility of production of hidden bottom pentaquark Pb states via γp and π−p scatterings. Because such states are still not observed in experiment, we need the theoretical decay width to make the prediction. One notices that in a recent paper [35], the authors predicted a series of hidden-bottom pentaquark states based on the observed three Pc states within the hadron molecular state model, and the decay widths of these states into the Υp channel were provided in their work.
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