Electroproduction ofρandϕMesons

Abstract

We report measurements of ${\rho }^0$ and $\varphi$ electroproduction at 19.5 GeV in a wide-aperture spectrometer which detected the scattered electron and the decay products of the vector mesons. As $\left|q^2\right|$ increases, the $\rho$ mass spectrum shape changes, the momentum-transfer distribution broadens, and the ratio of the $\rho$ cross section to the total cross section decreases. The ratio of longitudinally to transversely polarized ${\rho }^0$ mesons is ${0.45}_{-0.10\mathrm{}}^{+0.15\mathrm{}}$ at $\left|q^2\right|=m{\rho }^2$, and the interference between longitudinal and transverse amplitudes is almost maximal. The relative $\varphi$-meson cross section also decreases as $\left|q^2\right|$ increases.