Single spin asymmetry of vector meson production in the string model

Azimuthal asymmetry of vector-meson production in single-transversely polarized proton-proton collisions ($p\up p$) is calculated in a model based on the string fragmentation. The string is spanned by a valence quark of the projectile scattered on the target. The asymmetry is generated only during fragmentation of the scattered quark into hadrons. The obtained asymmetry of the $\rho$ mesons is opposite in sign to that of pions. On the other hand, if the asymmetry were generated during the quark scattering then the asymmetries of the vector and of the pseudoscalar mesons would be close to each other.