9-14 September 2018
University of Ferrara
Europe/Rome timezone
23RD INTERNATIONAL SPIN SYMPOSIUM

Measurements of polarization transfer to a bound proton in light nuclei by quasi-elastic scattering at MAMI

10 Sep 2018, 16:40
20m
A8 (Polo degli Adelardi - Via Adelardi, 33)

A8

Polo degli Adelardi - Via Adelardi, 33

Via Adelardi, 33
Parallel Sessions Spin Physics in Nuclear Reactions and Nuclei Spin physics in Nuclear Reactions and Nuclei

Speaker

Prof. Israel Mardor (Tel Aviv University, Tel Aviv, Israel)

Description

I will report on recent polarization transfer experiments carried out at the Mainz Microtron (MAMI), via the quasi-elastic A(e ⃗,e^' p ⃗ ) reaction, over a wide range of missing momentum and virtuality. We measured the ratio (Px/Pz)A of the transverse to longitudinal components of polarization transferred from an electron to a bound proton in 2H and 12C [1, 2] , and transverse (Px and Py) and longitudinal (Pz) components of the polarization transfer to a bound proton in 2H [3]. We observed consistent deviations from unity of the above ratio normalized to the free-proton ratio, (Px/Pz)A/(Px/Pz)1H, for both s-and p-shell knocked out protons, even though they are embedded in averaged local densities that differ by about a factor of two. The dependence of the double ratio on proton virtuality is similar to the one for knocked out protons from 2H and previous 4He data, suggesting a universal behavior, which seems to be independent of nuclear size, density and Q2. A precise determination of the electron beam polarization, along with a novel analysis method [4], enabled a detailed comparison of the measured polarization transfer components to a bound proton in 2H to a state-of-the-art calculation, which uses free-proton electromagnetic form factors. We observe very good agreement between the measured and the calculated (Px/Pz)2H ratios, but deviations of the individual components. Our results cannot be explained by medium modified electromagnetic form factors (FFs), unless the GE/GM ratio is kept intact. Excluding FF modifications, these deviations point to an incomplete description of the nuclear reaction mechanism in the calculation. References [1] I. Yaron, D. Izraeli, et al., Phys. Lett. B769 (2017) 21-24 [2] D. Izraeli, T. Brecelj, et al., Phys. Lett. B781 (2018) 95-98 [3] D. Izraeli, I. Yaron, B. S. Schlimme, et al., Phys. Lett. B781 (2018) 107-111 [4] D. Izraeli, I. Mardor, et al., arXiv:1803.06729 (2018)

Primary author

Prof. Israel Mardor (Tel Aviv University, Tel Aviv, Israel)

Presentation Materials