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

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) over right arrow, e'(p) over right arrow) 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. (C) 2018 The Author(s). Published by Elsevier B.V.