Towards clarifying the possibility of observation of the LHCb hidden-charm pentaquarks $P_c^{+}(4312)$, $P_c^{+}(4337)$, $P_c^{+}(4440)$ and $P_c^{+}(4457)$ in near-threshold charmonium photoproduction off protons and nuclei

Abstract

We study the near-threshold $J/\psi$ meson photoproduction from protons and nuclei by considering incoherent direct non-resonant ($\gamma p\to J/\psi p$, $\gamma n\to J/\psi n$) and two-step resonant ($\gamma p\to P_{ci}^{+}\to J/\psi p$, $\gamma n\to P_{ci}^0\to J/\psi n$, $i=1$, 2, 3, 4; $P_{c1}^{+,0}=P_c^{+,0}(4312)$, $P_{c2}^{+,0}=P_c^{+,0}(4337)$, $P_{c3}^{+,0}=P_c^{+,0}(4440)$, $P_{c4}^{+,0}=P_c^{+,0}(4457)$) charmonium production processes. We calculate the absolute excitation functions, energy and momentum distributions for the non-resonant, resonant and for the combined (non-resonant plus resonant) production of $J/\psi$ mesons on protons as well as, using the nuclear spectral function approach, on carbon and tungsten target nuclei at near-threshold incident photon energies by assuming the spin-parity assignments of the hidden-charm resonances $P_c^{+,0}(4312)$, $P_c^{+,0}(4337)$, $P_c^{+,0}(4440)$ and $P_c^{+,0}(4457)$ as $J^P=(1/2{)}^{-}$, $J^P=(1/2{)}^{-}$, $J^P=(1/2{)}^{-}$ and $J^P=(3/2{)}^{-}$ within three different realistic scenarios for the branching ratios of their decays to the $J/\psi p$ and $J/\psi n$ modes (0.25, 0.5 and 1%). We show that will be very hard to measure the $P_{ci}^{+}$ pentaquark states through the scan of the $J/\psi$ total photoproduction cross section on a proton target in the near-threshold energy region around the resonant photon energies of 9.44, 9.554, 10.04 and 10.12 GeV if these branching ratios $\sim$ 1% and less. We also demonstrate that at these photon beam energies the $J/\psi$ energy and momentum combined distributions considered reveal distinct sensitivity to the above scenarios, respectively, at "low" $J/\psi$ total energies and momenta, which implies that they may be an important tool to provide further evidence for the existence of the pentaquark $P_{ci}^{+}$ and $P_{ci}^0$ resonances.

26 pages

References in corpus (3)

• Deciphering the mechanism of near-threshold $J/\psi$ photoproduction
• The possibility to study in-medium modification of $J/\psi$ mesons from their photoproduction on nuclei near threshold in the case of presence of the LHCb pentaquark states $P_c^{+}$ in this photoproduction
• Regarding the possibility to observe the LHCb hidden-charm strange pentaquark $P_{cs}(4459{)}^0$ in antikaon-induced $J/\psi$ meson production on protons and nuclei near the $J/\psi$$\Lambda$ production threshold

Cited by in corpus (2)

• On the possibility of testing the two-peak structure of the LHCb hidden-charm strange pentaquark $P_{cs}(4459{)}^0$ in near-threshold antikaon-induced charmonium production on protons and nuclei
• Probing the hidden-bottom pentaquark resonances in photonuclear bottomonium production near threshold: differential observables