The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic (e)over-right-arrowp and quasi-elastic (e)over-right-arrowA scattering

A comparison between polarization -transfer to a bound proton in quasi -free kinematics by the A((e) over right arrow, e'(p) over right arrow) knockout reaction and that in elastic scattering off a free proton can provide information on the characteristics of the bound proton. In the past the reported measurements have been compared to those of a free proton with zero initial momentum. We introduce, for the first time, expressions for the polarization-transfer components when the proton is initially in motion and compare them to the H-2 data measured at the Mainz Microtron (MAMI). We show the ratios of the transverse (P-x) and longitudinal (P-z) components of the polarization transfer in H-2((e) over right arrow, e'(p) over right arrow )n, to those of elastic scattering off a "moving proton", assuming the proton's initial (Fermi -motion) momentum equals the negative missing momentum in the measured reaction. We found that the correction due to the proton motion is up to 20% at high missing momentum. However the effect on the double ratio (P-x/P-z)(A)/(P-x/P-z)(1H) is largely canceled out, as shown for both H-2 and C-12 data. This implies that the difference between the resting- and the moving -proton kinematics is not the primary cause for the deviations between quasi-elastic and elastic scattering reported previously. (C) 2019 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).