Abstract:A comparison between polarization-transfer to a bound proton in quasi-free kinematics by the A( e, e p) 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 2 H data measur… Show more
“…The dependence of the polarization transfer components and their ratios on Q 2 (due to the form factors) and other kinematic effects are reduced by dividing the measured values by the expected ones for elastic ep scattering with similar kinematics [13][14][15]27]. We use the "moving-proton" prescription [27,28], rather than the expressions for elastic scattering off a resting proton [10]. In this prescription, each measured quasi-elastic event is compared to an elastic event that has the same incident electron energy (k 0 ), the same magnitude of the four-momentum transfer (Q 2 ), and the same initial proton momentum (− p miss ) as the measured quasi-elastic event.…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…In this prescription, each measured quasi-elastic event is compared to an elastic event that has the same incident electron energy (k 0 ), the same magnitude of the four-momentum transfer (Q 2 ), and the same initial proton momentum (− p miss ) as the measured quasi-elastic event. Full details on the expressions for the polarization transfer observables are given in [27,28]. In Fig.…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…More details are found in the supplementary. [27,28] to those for free resting protons [10], using the kinematics derived from measured events in 2 H( e, e p)n reactions reported in this work (closed symbols) and in [13,14] (open symbols).…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…Following the convention used in [13][14][15]27] we use the struck-proton virtuality ("off-shellness"), ν, as our parameter of choice. The virtuality is defined as [13]:…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…We extracted the ratios of the polarization-transfer components for the deuteron to those of a free proton, (Px) (Px/Pz) 1 H , where the denominator expressions are calculated event-by-event using free moving-proton kinematics [27,28]. These ratios are shown as functions of ν in Fig.…”
We present measurements of the polarization-transfer components in the 2 H( e, e p) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, p miss , 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. 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 (Px/Pz) A (Px/Pz) 1 H is maintained in the positive missing-momentum region.
“…The dependence of the polarization transfer components and their ratios on Q 2 (due to the form factors) and other kinematic effects are reduced by dividing the measured values by the expected ones for elastic ep scattering with similar kinematics [13][14][15]27]. We use the "moving-proton" prescription [27,28], rather than the expressions for elastic scattering off a resting proton [10]. In this prescription, each measured quasi-elastic event is compared to an elastic event that has the same incident electron energy (k 0 ), the same magnitude of the four-momentum transfer (Q 2 ), and the same initial proton momentum (− p miss ) as the measured quasi-elastic event.…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…In this prescription, each measured quasi-elastic event is compared to an elastic event that has the same incident electron energy (k 0 ), the same magnitude of the four-momentum transfer (Q 2 ), and the same initial proton momentum (− p miss ) as the measured quasi-elastic event. Full details on the expressions for the polarization transfer observables are given in [27,28]. In Fig.…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…More details are found in the supplementary. [27,28] to those for free resting protons [10], using the kinematics derived from measured events in 2 H( e, e p)n reactions reported in this work (closed symbols) and in [13,14] (open symbols).…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…Following the convention used in [13][14][15]27] we use the struck-proton virtuality ("off-shellness"), ν, as our parameter of choice. The virtuality is defined as [13]:…”
Section: Measured Polarization-transfermentioning
confidence: 99%
“…We extracted the ratios of the polarization-transfer components for the deuteron to those of a free proton, (Px) (Px/Pz) 1 H , where the denominator expressions are calculated event-by-event using free moving-proton kinematics [27,28]. These ratios are shown as functions of ν in Fig.…”
We present measurements of the polarization-transfer components in the 2 H( e, e p) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, p miss , 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. 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 (Px/Pz) A (Px/Pz) 1 H is maintained in the positive missing-momentum region.
We present the findings of a study based on a new inelastic electron-scattering experiment on the $${}^{12}$$
12
C nucleus focusing on the kinematic region of $$Q^2=0.8\,\textrm{GeV}^2/{c}^2$$
Q
2
=
0.8
GeV
2
/
c
2
. The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10$$\%$$
%
.
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