High precision measurement of phi-nucleon cross section using a tensor polarized deuteron target

Abstract

We propose to measure the $\phi$-nucleon cross section $\sigma_{\phi N}$ to solve the longstanding puzzle of whether $\sigma_{\phi N} \simeq 10$ mb, as extracted from photoproduction, or $\sim$30 mb, as obtained from nuclear rescattering. CLAS data demonstrated that even precision data for unpolarized $\phi$ photoproduction are insufficient to unambiguously extract $\sigma_{\phi N}$, allowing the possibilities of both $\sigma_{\phi N}$ values. However, as it often happens, the additional spin degrees of freedom afforded by a polarized target sufficiently constrains the theory to unambiguously provide $\sigma_{\phi N}$. This will be accomplished with a measurement of the tensor asymmetry $A_{zz}$ in coherent $\phi$ photoproduction from the deuteron, $\gamma + d \to \phi + d$. The same measurement in coherent $\rho$ photoproduction will allow us to understand the kinematic dependence of the photon longitudinal interaction length for this process, which is necessary to identify unambiguous signal for color transparency. This will be the first study of observables in photoproduction from tensor polarized deuterons. We will use the standard GlueX spectrometer, the Hall D Dynamic Nuclear Polarization (DNP) polarized target, and both a circularly and linearly polarized tagged photon beam. The ability to operate the target in a frozen spin mode and produce negative tensor-polarization will decrease the time needed to make the measurements by a factor of more than 2.5. We request 65 days of beam time which includes commissioning the tensor polarized target.