The near-threshold pion-induced \(\phi\) production off nuclei has been studied in the kinematical conditions of the HADES experiment using a collision model based on the nuclear spectral function. ...Starting from the elementary reaction \({\pi^-}p \to {\phi}n\), absolute differential and integral cross sections for the production of \(\phi\) mesons off a light carbon and a heavy tungsten target have been calculated and compared to the recently reported experimental cross sections. The absolute cross section values are shown to be sensitive to the effective nuclear scalar \(\phi\) and neutron potentials while the transparency ratio is governed by the \({\phi}N\) absorption cross section. The experimental data are found to be consistent with an attractive \({\phi}\)-nucleus potential of \(\approx\) -(50--100) MeV at normal nuclear matter density \(\rho_0\) and an effective \({\phi}N\) absorption cross section of \(\approx\) 12--25 mb. The extracted \(\phi\)-nucleus potential is deeper than previous theoretical and experimental findings as well as those obtained in the present work within the (\(t{\rho}\)) approximation with accounting for Pauli correlations from the spin-averaged \(\phi\)-\(p\) scattering length reported in a recent ALICE experiment.
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.
Within the spectator model, we study the reaction {gamma}d {sup {yields}} K{sup -}{theta}{sup +}p {sup {yields}} K{sup -}K{sup +}np in the threshold energy region. We present the predictions for the ...exclusive and inclusive K{sup -}-meson angular distributions in the laboratory system for this reaction calculated for two possible parity states of the {theta}{sup +} resonance at 1.5-and 1.75-GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where the contribution from the main background sources, associated with the {phi}(1020), {lambda}(1520) production as well as with the K{sup -}p rescattering in the final state, is expected to be dominant. We show that, under the chosen kinematics, these distributions are sensitive to the {theta}{sup +} parity and, therefore, can be used as a filter for the determination of its parity.
Chinese Physics C Vol.42, No.8 (2018) 084101 We study the near-threshold pion-induced production of $\phi$ mesons off
nuclei in the kinematical conditions of the HADES experiment, recently
performed ...at GSI. The calculations have been performed within a collision model
based on the nuclear spectral function. The model accounts for both the primary
$\pi^-$ meson--proton ${\pi^-}p \to {\phi}n$ and the secondary pion--nucleon
${\pi}N \to {\phi}N$ $\phi$ production processes as well as the effects of the
nuclear $\phi$ and nucleon mean-field potentials. We find that the primary
reaction channel ${\pi^-}p \to {\phi}n$ dominates in the $\phi$ production off
$^{12}$C and $^{184}$W target nuclei in the HADES acceptance window at incident
pion momentum of 1.7 GeV/c. We calculate the momentum dependence of the
absolute and relative (transparency ratio) $\phi$ meson yields from the above
direct channel. The calculations have been performed for this initial pion
momentum allowing for different options for the ${\phi}N$ absorption cross
section $\sigma_{{\phi}N}$ and different scenarios for the in-medium mass
shifts of the $\phi$ meson and secondary neutron, produced together with $\phi$
in this channel. We demonstrate that the transparency ratio for the $\phi$
mesons has, contrary to the absolute cross sections, an insignificant
sensitivity to the $\phi$ meson and secondary neutron in-medium mass shifts at
$\phi$ momenta studied in the HADES experiment. On the other hand, we show that
there are measurable changes in the transparency ratio due to the ${\phi}N$
absorption cross section, which means that such relative observable can be
useful to help determine this cross section from the data taken in the HADES
experiment.
We study the near-threshold \(J/\psi\) meson production on protons and nuclei by considering incoherent direct non-resonant \(K^-p \to {J/\psi}\Lambda\) and two-step resonant \({K^-}p \to ...P_{cs}(4459)^0 \to {J/\psi}\Lambda\) 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 off protons as well as off carbon and tungsten target nuclei at near-threshold incident antikaon energies by considering these elementary production channels as well as by assuming the spin-parity assignment of the hidden-charm resonance \(P_{cs}(4459)^0\) with strangeness as \(J^P=(3/2)^-\) within six different scenarios for the branching ratio \(BrP_{cs}(4459)^0 \to {J/\psi}\Lambda\) of the decay \(P_{cs}(4459)^0 \to {J/\psi}\Lambda\). We show that the combined observables considered reveal definite sensitivity to these scenarios, which means that they may be an important tool to provide further evidence for the existence of the pentaquark \(P_{cs}(4459)^0\) resonance and to get valuable information on its decay rate to the \({J/\psi}\Lambda\) final state. Their measurements could be performed in the future at the J-PARC Hadron Experimental Facility.
We study the near-threshold inclusive photoproduction of \(\Xi^-\) hyperons off \(^{12}\)C and \(^{184}\)W target nuclei within a first-collision model relying on the nuclear spectral function and ...including incoherent \(\Xi^-\) production in direct elementary \({\gamma}p \to K^+{K^+}\Xi^-\) and \({\gamma}n \to K^+{K^0}\Xi^-\) processes. The model takes into account the impact of the nuclear effective scalar \(K^+\), \(K^0\), \(\Xi^-\) and their Coulomb potentials on these processes as well as the absorption of final \(\Xi^-\) hyperons in nuclear matter, the binding of intranuclear nucleons and their Fermi motion. We calculate the absolute differential cross sections and their ratios for the production of \(\Xi^-\) hyperons off these nuclei at laboratory polar angles \(\le\) 45\(^{\circ}\) by photons with energies of 2.5 and 3.0 GeV, with and without imposing the phase space constraints on the \(\Xi^-\) emission angle in the respective \({\gamma}p\) center-of-mass system. We also calculate the momentum dependence of the transparency ratio for \(\Xi^-\) hyperons for the \(^{184}\)W/\(^{12}\)C combination at these photon energies. We show that the \(\Xi^-\) momentum distributions (absolute and relative) at the adopted initial photon energies possess, contrary to the transparency ratio for \(\Xi^-\) hyperons, a definite sensitivity to the considered changes in the scalar \(\Xi^-\) nuclear mean-field potential at saturation density \(\rho_0\) in the low-momentum range of 0.1--0.8 GeV/c. Therefore, the precise measurements of these distributions in a dedicated experiment at the CEBAF facility will provide valuable information on the \(\Xi^-\) in-medium properties, which will be supplementary to that inferred from studying of the (\(K^-\),\(K^+\)) reactions at initial momenta of 1.6--1.8 GeV/c.
We study the antikaon-induced inclusive cascade \(\Xi^-\) hyperon production from \(^{12}\)C and \(^{184}\)W target nuclei near threshold within a nuclear spectral function approach. The approach ...describes incoherent direct \(\Xi^-\) hyperon production in elementary \({K^-}p \to {K^+}\Xi^-\) and \({K^-}n \to {K^0}\Xi^-\) processes as well as takes into account the influence of the scalar nuclear \(K^-\), \(K^+\), \(K^0\), \(\Xi^-\) and their Coulomb potentials on these processes. We calculate the absolute differential and total cross sections for the production of \(\Xi^-\) hyperons off these nuclei at laboratory angles \(\le\) 45\(^{\circ}\) by \(K^-\) mesons with momenta of 1.0 and 1.3 GeV/c, which are close to the threshold momentum (1.05 GeV/c) for \(\Xi^-\) hyperon production on the free target nucleon at rest. We also calculate the momentum dependence of the transparency ratio for the \(^{184}\)W/\(^{12}\)C combination for \(\Xi^-\) hyperons at these \(K^-\) beam momenta. We show that the \(\Xi^-\) differential and total (absolute and relative) production cross sections at the considered initial momenta reveal a distinct sensitivity to the variations in the scalar \(\Xi^-\) nuclear potential at saturation density \(\rho_0\), studied in the paper, in the low-momentum region of 0.1--0.6 GeV/c. We also demonstrate that for the subthreshold \(K^-\) meson momentum of 1.0 GeV/c there is a strong sensitivity of the transparency ratio for \(\Xi^-\) hyperons to the considered changes in the \(\Xi^-\) nuclear potential at all outgoing \(\Xi^-\) momenta as well. Therefore, the measurement of these absolute and relative observables in a dedicated experiment at the J-PARC will provide valuable information on the \(\Xi^-\) in-medium properties, which will be complementary to that deduced from the study of the inclusive (\(K^-\),\(K^+\)) reactions at incident momenta of 1.6--1.8 GeV/c in the \(\Xi^-\) bound and quasi-free regions.
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