Φ-meson Photoproduction and Strangeness of the Nucleon

The possible existence of hidden strangeness in the nucleon has been one of the most controversial problems in hadron physics. Some experimental results have been interpreted as signatures of hidden strangeness of the nucleon, but it has been also claimed that these experiments could be understood with little or null strangeness in the nucleon. It will be interesting, therefore, to study other processes that might be related directly to the hidden nucleon strangeness. One of them is to use φ production from the proton. Since the φ is nearly pure ss̄ state, its coupling to the proton is suppressed by the OZI rule. Then the idea is that studying the strange sea quark contribution through the OZI evasion processes may give informations about the hidden strangeness of the nucleon. In this work, we discuss φ photoproduction process from the proton targets (Fig. 1). We define k, q, p, and p as the four-momenta of the photon, φ-meson, target proton, and recoiled proton, respectively, and t = (p − p) and W 2 = (p + k). The scattering angle in c.m. frame is denoted by θ. In this case, the main contribution to the cross section is from the diffractive production process of vector-meson dominance (VDM), and the one-pion-exchange (OPE) process comes in as a correction to VDM. This OPE process is possible because of the φ-π-γ coupling, and represents the contributions from the (small) non-strange quark components of the φ-meson.