Is the nonmonotonic behavior in the cross section of phi photoproduction near threshold a signature of a resonance?

Abstract

We study whether the nonmonotonic behavior found in the differential cross section of the phi-meson photoproduction near threshold can be described by a resonance. Namely, we add a resonance to a model consisting of Pomeron and (pi,eta) exchange by fiat and see if, with a suitable assignment of spin and parity, mass and width, as well as the coupling constants, one would be able to obtain a good description to all the data reported by the LEPS collaboration in the low-energy region. The resonant contribution is evaluated by using an effective Lagrangian approach. We find that, with the assumption of a J^P=3/2^- resonance with mass of 2.10 +- 0.03 GeV and width of 0.465 +- 0.141 GeV, LEPS data can indeed be well described. The ratio of the helicity amplitudes A_(1/2)/A_(3/2) calculated from the resulting coupling constants differs in sign from that of the known D13(2080). We further find that the addition of this postulated resonance can substantially improve the agreement between the existing theoretical predictions and the recent omega photoproduction data if a large value of the OZI evading parameter x_OZI = 12 is assumed for the resonance.