Production of spin-3 mesons in diffractive DIS
We calculate the amplitudes of J^{PC}=3^{--} meson production in diffractive DIS within the k_t-factorization approach, with a particular attention paid to the rho_3(1690) meson. We find that at all Q^2 the rho_3(1690) production cross section is 2-5 times smaller than the rho(1700) production cross section, which is assumed to be a pure D-wave state. Studying sigma_L and sigma_T separately, we observe domination of rho_3 in sigma_L and domination of rho(1700) in sigma_T and offer an explanation of this behavior in simple terms. We also find very strong contributions -- sometimes even domination -- of the s-channel helicity violating amplitudes. The typical color dipole sizes probed in rho_3 production are shown to be larger than those in the ground state rho production, and the energy dependence of rho_3 cross section turns out to be much flatter than the rho production cross section. All the conclusions about the relative behavior of rho_3(1690) and rho(1700) mesons are numerically stable against variations of input parameters.