The Q^2-Dependence of Nuclear Transparency for Exclusive $\rho^0$ Production

TL;DR

This study investigates how nuclear transparency in exclusive $ ho^0$ meson production varies with coherence length and $Q^2$, providing evidence for color transparency effects in nuclear matter.

Contribution

It presents the first detailed measurement of the $Q^2$ dependence of nuclear transparency for $ ho^0$ production, confirming theoretical predictions of color transparency.

Findings

Nuclear transparency increases with $Q^2$ for both coherent and incoherent production.

Transparency varies with coherence length, increasing for coherent and decreasing for incoherent processes.

Results agree with color transparency theoretical models.

Abstract

Exclusive coherent and incoherent electroproduction of the $\rho^0$ meson from $^1$H and $^{14}$N targets has been studied at the HERMES experiment as a function of coherence length ($l_c$), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon ($-Q^2$). The ratio of $^{14}$N to $^1$H cross sections per nucleon, known as nuclear transparency, was found to increase (decrease) with increasing coherence length for coherent (incoherent) $\rho^0$ electroproduction. For fixed coherence length, a rise of nuclear transparency with $Q^2$ is observed for both coherent and incoherent $\rho^0$ production, which is in agreement with theoretical calculations of color transparency.