Spin Density Matrix Elements from diffractive $\phi$ meson production at HERMES

TL;DR

This paper measures spin density matrix elements in exclusive $$ meson production at HERMES, revealing s-channel helicity conservation and no significant unnatural-parity contributions in the studied kinematic range.

Contribution

It provides the first detailed measurement of spin density matrix elements for $$ meson production in this kinematic region, confirming helicity conservation.

Findings

Data consistent with s-channel helicity conservation.

No significant unnatural-parity-exchange amplitudes detected.

Spin density matrix elements depend on $Q^{2}$ and $t$.

Abstract

Exclusive production of $\phi$ mesons on hydrogen and deuterium targets is studied in the HERMES kinematic region $1 < Q^{2} < 7$ GeV$^2$ and $3.0 < W < 6.3$ GeV. Spin density matrix elements and their $Q^{2}$ and $t$ dependences are presented. These data are consistent with s-channel helicity conservation in exclusive $\phi$ meson production. No significant evidence for the contribution of unnatural-parity-exchange amplitudes is found.