Abstract

We report measurements of the induced polarization P→ of protons knocked out from 2H and 12C via the A(e,ep→) reaction. We have studied the dependence of P→ on two kinematic variables: the missing momentum pmiss and the “off-coplanarity” angle ϕpq between the scattering and reaction planes. For the full 360° range in ϕpq, both the normal (Py) and, for the first time, the transverse (Px) components of the induced polarization were measured with respect to the coordinate system associated with the scattering plane. Px vanishes in coplanar kinematics, however in non-coplanar kinematics, it is on the same scale as Py. We find that the dependence on ϕpq is sine-like for Px and cosine-like for Py. For carbon, the magnitude of the induced polarization is especially large when protons are knocked out from the p3/2 shell at very small pmiss. For the deuteron, the induced polarization is near zero at small |pmiss|, and its magnitude increases with |pmiss|. For both nuclei such behavior is reproduced qualitatively by theoretical results, driven largely by the spin-orbit part of the final-state interactions. However, for both nuclei, sizeable discrepancies exist between experiment and theory.

Original languageEnglish
Article number135984
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume811
DOIs
StatePublished - 10 Dec 2020

Funding

FundersFunder number
Israel Academy of Arts and Sciences
Israel Ministry of Science, Technology and Spaces
U.S. National Science Foundation
National Science Foundation2017630, PHY-1505615, PHY-1205782
National Science Foundation
United States - Israel Binational Science Foundation
Deutsche Forschungsgemeinschaft
United States-Israel Binational Science Foundation
Israel Science Foundation951/19, 390/15
Israel Science Foundation
Javna Agencija za Raziskovalno Dejavnost RSP1–0102
Javna Agencija za Raziskovalno Dejavnost RS
Hrvatska Zaklada za Znanost8570
Hrvatska Zaklada za Znanost
Ministry of Science and Technology, Israel
PAZY Foundation294/18
PAZY Foundation

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