Nucleon resonances in theγp→ϕK+Λreaction near threshold

Abstract

We investigate the γp → φK + Λ reaction near threshold within an effective Lagrangian approach and the isobar model. Various nucleon resonances caused by the π and η meson exchanges and background contributions are considered. It is shown that the contribution from the N * (1535) resonance caused by the η meson exchange plays the predominant role. Hence, this reaction provides a good new platform to study the N * (1535) resonance. The predicted total cross section and specific features of angular distributions can be tested by future experiments.PACS numbers: 13.75.-n.; 14.20.Gk.; 13.30.Eg.

ϕ(2170) production in the process γp→ηϕp

“…With the above formalisms, we calculate the total and differential cross sections for the γp → ηφp reaction by using a Monte Carlo multi-particle phase space integration program used in Refs. [41,57].…”

“…with the coupling constants g πN N = 13.45 and g ηN N = 2.24, taken from Refs. [40][41][42]. For the γφπ and γφη couplings, we take the interaction Lagrangian densities as used in Refs.…”

“…For the intermediate nucleon excited resonances, we only take into account the contribution of the resonances N (1535), since the ηp production from the intermediate resonance N (1535) plays the dominant role near the threshold, as discussed in Refs. [41,44] where more nucleon excited resonances were considered. We also need the interaction Lagrangian densities involving N (1535) (marked as N * ) [45],…”

“…In our present calculation, we use the cutoff parameters Λ π = Λ η = 1.5 GeV, and Λ N = Λ N * = 2.0 GeV for N and N (1535) as used in Refs. [41,42]. For the one of φ(2170), we take Λ φ * = 1.0 GeV.…”

“…q π = p 1 − p 3 is the four-momentum for the exchanged π meson, and q R = p 4 + p 5 is the four-momentum for intermediate N and N (1535). It is easy to show that the above amplitudes respect the gauge invariance [41]. Then the differential cross section for the reaction γp → ηφp can be expressed as,…”