Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence

Abstract We measured the ratio P x / P z of the transverse to longitudinal components of polarization transferred from electrons to bound protons in C 12 by the C 12 ( e → , e ′ p → ) process at the Mainz Microtron (MAMI). We observed consistent deviations from unity of this ratio normalized to the free-proton ratio, ( P x / P z ) C 12 / ( P x / P z ) H 1 , for both s - and p -shell knocked out protons, even though they are embedded in averaged local densities that differ by about a factor of two. The dependence of the double ratio on proton virtuality is similar to the one for knocked out protons from H 2 and He 4 , suggesting a universal behavior. It further implies no dependence on average local nuclear density.