Double-spin asymmetries in the cross section of $\rho^0$ and $\phi$ production at intermediate energies

TL;DR

This study measures double-spin asymmetries in electroproduction of $ ho^0$ and $phi$ mesons, revealing a positive asymmetry for $ ho^0$ on the proton and zero asymmetries elsewhere, supporting specific theoretical models.

Contribution

First measurement of double-spin asymmetries in $ ho^0$ and $phi$ electroproduction at intermediate energies, providing experimental evidence for unnatural parity exchange contributions.

Findings

Positive asymmetry observed in $ ho^0$ on proton

Asymmetries on deuteron and for $phi$ are consistent with zero

Results support models involving unnatural parity exchange and $sar{s}$ knockout

Abstract

Double-spin asymmetries in the cross section of electroproduction of $\rho^0$ and $\phi$ mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive $\rho^0$ electroproduction on the proton exhibits a positive tendency. This is consistent with theoretical predictions that the exchange of an object with unnatural parity contributes to exclusive $\rho^0$ electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in $\rho^0$ and $\phi $ meson electroproduction by quasi-real photons were also found to be consistent with zero; the asymmetry in the case of the $\phi$ meson is compatible with a theoretical prediction which involves $s\bar{s}$ knockout from the nucleon.