Pomeron, nucleon-resonance, and (0+,0−,1+) -meson contributions in ϕ -meson photoproduction

Abstract

We investigate the reaction mechanism of the φ-meson photoproduction off the proton target, i.e., γp → φp, up to √ s = 2.8 GeV. For this purpose, we employ an effective Lagrangian approach in the tree-level Born approximation, and we employ various experimental and theoretical inputs. As a theoretical setup, the vectorlike Pomeron (C = +1) is taken into account as a parameterized two-gluon exchange contribution. We also consider f1(1285) axial-vector-meson, (π, η) pseudoscalarmeson, and (a0, f0) scalar-meson exchanges in the t channel, in addition to the experimentally confirmed nucleon resonances, such as N * (2000, 5/2 + ) and N * (2300, 1/2 + ), for the direct φ-meson radiations in the s and u channels. We provide numerical results for the total and differential cross sections as well as the spin-density matrices in the Gottfried-Jackson, Adair, and helicity frames. We observe that, together with the universally accepted pomeron contribution, the considered meson and nucleon-resonance contributions play significant roles in reproducing the experimental data for the forward and backward φ-meson scattering-angle regions, respectively, indicating the nontrivial interferences between mesonic and baryonic contributions.

Searching for the odderon in pp→ppK+K− and pp→pLebiedowicz1, Nachtmann2, Szczurek3 2020Phys. Rev. D180260View full textAdd to dashboardCite

“…There the nondiffractive processes of the pseudoscalar π 0 -and η-meson exchange are known to contribute and are not negligible due to constructive η-π 0 interference; see, e.g., [64,65]. In addition, many other processes, e.g., direct ϕ meson radiation via the s-and u-channel proton exchanges [64,71], ss-cluster knockout [63], t-channel σ-, f 2 ð1270Þand f 1 ð1285Þ-exchanges [70] were considered. In [70] no vertex form factors were taken into account for the Reggeized meson exchange contributions and instead of the f 2 ð1270Þ-exchange there one should consider f 0 2 -exchange with appropriate parameters.…”

“…However, a peak in the differential cross sections ðdσ=dtÞ t¼t min at forward angles around E γ ∼ 2 GeV (W γp ∼ 2.3 GeV) observed by the LEPS [97,98] and CLAS [99] collaborations cannot be explained by the processes mentioned above. To explain the near-threshold bump structure the authors of [67,68,71] propose to include exchanges with the excitation of nucleon resonances. In [66,69] another explanation, using the coupled-channel contributions with the Λð1520Þ resonance, was investigated.…”

“…For this purpose we have to consider also lowenergy photon-proton collisions in the γp → ϕp reaction where the corresponding mechanism is not well established yet; see, e.g., Refs. [62][63][64][65][66][67][68][69][70][71]. Of course, the amplitude for γp → ϕp cannot be realized by the C ¼ −1 odderon exchange.…”

Dynamical model of $ϕ$ meson photoproduction on the nucleon and $^4He$

“…We follow the model of Ref. [28] for the 𝛾𝑁 → 𝑁 * → 𝜙𝑁 cross sections to include 𝑁 * (2000, 5/2 + ) and 𝑁 * (2300, 1/2 + ).…”

“…In the near threshold energy region, however, the mechanisms arising from mesonexchanges and the excitation of nucleon resonances (𝑁 * ) in the 𝜙𝑁 channel would give non-negligible contributions as demonstrated in Refs. [25][26][27][28][29]. In the present work, we follow the model of Refs.…”