State Photoproduction

It is shown that the list of unusual mesons planned for a careful study in photoproduction can be extended by the exotic states X(1600) with I(J) = 2(2) which should be looked for in the ρρ decay channels in the reactions γN → ρρN and γN → ρρ∆. The full classification of the ρρ states by their quantum numbers is presented. A simple model for the spin structure of the γp → f2(1270)p, γp → a2(1320)p, and γN → X(N, ∆) reaction amplitudes is formulated and the tentative estimates of the corresponding cross sections at the incident photon energy Eγ ≈ 6 GeV are obtained: σ(γp → f2(1270)p) ≈ 0.12 μb, σ(γp → a2(1320)p) ≈ 0.25 μb, σ(γN → XN → ρρN) ≈ 0.018 μb, and σ(γp → X∆ → ρρ∆) ≈ 0.031 μb. The problem of the X signal extraction from the natural background due to the other ππππ production channels is discussed. In particular the estimates are presented for the γp → h1(1170)πn, γp → ρn → ππππn, and γp → ωρp reaction cross sections. Our main conclusion is that the search for the exotic X(2(2)) states is quite feasible at JEFLAB facility. The expected yield of the γN → XN → ρρN events in a 30-day run at the 100% detection efficiency approximates 2.8× 10 events. PACS number(s): 13.60.Le, 12.40.Nn, 14.40.Ev email: [email protected] email: [email protected]