Measurement of elastic electroproduction of phi mesons at HERA

TL;DR

This paper reports on the measurement of elastic phi meson electroproduction at HERA, analyzing cross sections, polarization states, and s-channel helicity conservation violations across various photon virtualities and energies.

Contribution

It provides the first detailed analysis of phi meson electroproduction, including polarization and SCHC violation, and compares results with other vector mesons scaled by quark charges.

Findings

Phi meson cross section agrees with other vector mesons when scaled

Observed a small violation of s-channel helicity conservation

Detailed polarization analysis of phi mesons

Abstract

The elastic electroproduction of phi mesons is studied at HERA with the H1 detector for photon virtualities 1 < Q^2 < 15 GeV^2 and hadronic centre of mass energies 40 < W < 130 GeV. The Q^2 and t dependences of the cross section are extracted (t being the square of the four-momentum transfer to the target proton). When plotted as function of (Q^2 + M_V^2) and scaled by the appropriate SU(5) quark charge factor, the phi meson cross section agrees within errors with the cross sections of the vector mesons V = rho, omega and J/psi. A detailed analysis is performed of the phi meson polarisation state and the ratio of the production cross sections for longitudinally and transversely polarised phi mesons is determined. A small but significant violation of s-channel helicity conservation (SCHC) is observed.