Production of orbitally excited vector mesons in diffractive DIS [rapid communication]

Within the k_t-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the ρ (1450) / ρ (1700) case. At small Q², orbital excitation of light quarkonia is found to dominate over radial excitations in diffractive production. We predict strong suppression of the production of orbital excitations by longitudinal photons, which leads to very small σ_L /σ_T ratio. At small Q², the s-channel helicity violating transitions contribute ∼ 10- 15 % of the transverse cross section and ∼50% of the longitudinal cross section. We also study mixing between radial and orbital excitations and determine strategies towards clarification of S-wave/D-wave assignment to ρ (1450) and ρ (1700) mesons. The results are compared with the experimental data available, and predictions for future experiments are given.