Single spin asymmetry of vector meson production in the string model

TL;DR

This paper models the azimuthal asymmetry in vector meson production during polarized proton-proton collisions using string fragmentation, revealing opposite asymmetries for rho mesons compared to pions, and highlighting the fragmentation process as the asymmetry source.

Contribution

It introduces a string model-based calculation of single-spin asymmetry in vector meson production, emphasizing the role of fragmentation over scattering in asymmetry generation.

Findings

Asymmetry of rho mesons is opposite to that of pions.

Asymmetry arises during fragmentation, not scattering.

Model predicts different asymmetry signs for vector and pseudoscalar mesons.

Abstract

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.