Study of a possibility of observation of hidden-bottom pentaquark resonances in bottomonium photoproduction on protons and nuclei near threshold

Abstract

We study the ${\rm Y}(1S)$ meson photoproduction on protons and nuclei at the near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies $E_{\gamma }$ below 68.8 GeV). We calculate the absolute excitation functions for the non-resonant and resonant photoproduction of ${\rm Y}(1S)$ mesons off protons at incident photon laboratory energies of 63--68 GeV by accounting for direct ($\gamma p\to {\rm Y}(1S)p$) and two-step ($\gamma p\to P_b^{+}(11080,11125,11130)\to {\rm Y}(1S)p$) ${\rm Y}(1S)$ production channels within different scenarios for the non-resonant total cross section of elementary reaction $\gamma p\to {\rm Y}(1S)p$ and for branching ratios of the decays $P_b^{+}(11080,11125,11130)\to {\rm Y}(1S)p$. We also calculate an analogous functions for photoproduction of ${\rm Y}(1S)$ mesons on ${}^{12}$C and ${}^{208}$Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0--11.4 GeV by considering respective incoherent direct ($\gamma N\to {\rm Y}(1S)N$) and two-step ($\gamma p\to P_b^{+}(11080,11125,11130)\to {\rm Y}(1S)p$, $\gamma n\to P_b^0(11080,11125,11130)\to {\rm Y}(1S)n$) ${\rm Y}(1S)$ production processes within a nuclear spectral function approach. We show that a detailed scan of the ${\rm Y}(1S)$ total photoproduction cross section on a proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the U.S. and China should give a definite result for or against the existence of the non-strange hidden-bottom pentaquark states $P_{bi}^{+}$ and $P_{bi}^0$ ($i=$1, 2, 3) as well as clarify their decay rates.

Comments: 18 pages, Chinese Physics C, accepted for publication, in press. arXiv admin note: text overlap with arXiv:2003.00788