Elsevier

Physics Letters B

Volume 795, 10 August 2019, Pages 599-605
Physics Letters B

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

https://doi.org/10.1016/j.physletb.2019.07.002Get rights and content
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Abstract

We present measurements of the polarization-transfer components in the H2(e,ep) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, pmiss, up to 220MeV/c, and Q2=0.65 (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 Px and Pz 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 GE/GM at the level of a few percent. We also compare the measured polarization-transfer components and their ratio for 2H to those of a free (moving) proton. We find that the universal behavior of 2H, 4He and 12C in the double ratio (Px/Pz)A(Px/Pz)H1 is maintained in the positive missing-momentum region.

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Present address: MIT-LNS, Cambridge, MA 02139, USA.