Quasi-elastic polarization-transfer measurements on the deuteron in anti-parallel kinematics

Abstract

We present measurements of the polarization-transfer components in the ${}^2$H$(\vec{e},e^{\prime }\vec{p})$ reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, $p_{\mathrm{miss}}$, up to 220 MeV$/c$, and $Q^2=0.65$ $(\mathrm{GeV}/c{)}^2$. These measurements, performed at the Mainz Microtron (MAMI), were motivated by theoretical calculations which predict small final-state interaction (FSI) effects in these kinematics, making them favorable for searching for medium modifications of bound nucleons in nuclei. We find in this kinematic region that the measured polarization-transfer components $P_x$ and $P_z$ and their ratio agree with the theoretical calculations, which use free-proton form factors. Using this, we establish upper limits on possible medium effects that modify the bound proton's form factor ratio $G_E/G_M$ at the level of a few percent. We also compare the measured polarization-transfer components and their ratio for ${}^2$H to those of a free (moving) proton. We find that the universal behavior of ${}^2$H, ${}^4$He and ${}^{12}$C in the double ratio $\frac{(P_x/P_z{)}^A}{(P_x/P_z{)}^{{}^1\mathrm{H}}}$ is maintained in the positive missing-momentum region.

References in corpus (4)

• Nucleon Electromagnetic Form Factors
• Polarization Transfer in the 4He(e,e'p)3H Reaction at Q^2 = 0.8 and 1.3 (GeV/c)^2
• Proton G_E/G_M from beam-target asymmetry
• Polarization observables for elastic electron scattering off a moving nucleon