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.

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Cited by in corpus (5)

• Polarization transfer to bound protons measured by quasi-elastic electron scattering on ${}^{12}$C
• Comparison of recoil polarization in the ${}^{12}\mathrm{C}(\vec{e},e^{\prime }\vec{p})$ process for protons extracted from $s$ and $p$ shell
• Measurement of polarization transfer in the quasi-elastic ${}^{40}\mathrm{Ca}(\vec{e},e^{\prime }\vec{p})$ process
• Measurements of the electron-helicity asymmetry in the quasi-elastic $\mathrm{A}(\vec{e},e^{\prime }p)$ process
• Measurements of the induced polarization in the quasi-elastic $A(e,e^{\prime }\vec{p})$ process in non-coplanar kinematics