Abstract
We present measurements of the polarization-transfer components in the H2(e→,e′p→) 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.
Highlights
Polarization transfer from a polarized electron to a proton in elastic scattering has become a recognized method to measure the ratio of the proton’s elastic electromagnetic form factors, G E /G M [1,2,3,4,5,6,7,8,9]
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 )1mHoving ( (P z) and their ratio agree with the theoretical calculations, which use free-proton form factors
We present the measurements of P x and P z, and their ratio, in a previously unexplored kinematic region, where theoretical calculations predict that the FSI effects would be small compared to those in the kinematic regions of previous measurements (e.g. [13,14])
Summary
We present measurements of the polarization-transfer components in the 2H(e, e p) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, pmiss, up to 220 MeV/c, and Q 2 = 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 P x and P z and their ratio agree with the theoretical calculations, which use free-proton form factors. We find that the universal behavior of 2H, 4He and 12C in the double ratio (Px/Pz)A (P x /P z )1H is maintained in the positive missing-momentum region
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