Exclusive electroproduction of $\phi$ mesons at HERA

TL;DR

This paper reports on the measurement of exclusive $phi$ meson electroproduction at HERA, analyzing cross sections and polarization ratios across various kinematic variables, and comparing results with theoretical models.

Contribution

It provides new experimental data on $phi$ electroproduction at HERA, including cross sections and polarization ratios, and compares these with existing theoretical predictions.

Findings

Cross sections vary with $Q^2$, $W$, and $t$.

Ratios of longitudinal to transverse cross sections depend on $Q^2$ and $W$.

Data generally agree with theoretical models within uncertainties.

Abstract

Exclusive electroproduction of $\phi$ mesons has been studied in $e^\pm p$ collisions at $\sqrt{s}=318 \gev$ with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb$^{-1}$. The $\gamma^*p$ cross section is presented in the kinematic range $2<Q^2<70 \gev^2$, $35<W<145 \gev$ and ${|t|}<0.6 \gev^2$. The cross sections as functions of $Q^2$, $W$, $t$ and helicity angle $\theta_h$ are compared to cross sections for other vector mesons. The ratios $R$ of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of $Q^2$ and $W$. The data are also compared to predictions from theoretical models.