학술논문
Measurements of the electron-helicity asymmetry in the quasi-elastic ${\rm A}(\vec{e},e' p)$ process
Document Type
Working Paper
Author
Kolar, Tim; Paul, Sebouh J.; Achenbach, Patrick; Arenhövel, Hartmuth; Ashkenazi, Adi; Beričič, Jure; Böhm, Ralph; Bosnar, Damir; Brecelj, Tilen; Cline, Ethan; Cohen, Erez O.; Distler, Michael O.; Esser, Anselm; Friščić, Ivica; Gilman, Ronald; Giusti, Carlotta; Heilig, Matthias; Hoek, Matthias; Izraeli, David; Kegel, Simon; Klag, Pascal; Korover, Igor; Lichtenstadt, Jechiel; Mardor, Israel; Merkel, Harald; Middleton, Duncan G.; Mihovilovič, Miha; Müller, Julian; Müller, Ulrich; Olivenboim, Mor; Piasetzky, Eliezer; Pochodzalla, Josef; Ron, Guy; Schlimme, Björn S.; Schoth, Matthias; Schulz, Florian; Sfienti, Concettina; Širca, Simon; Spreckels, Rouven; Štajner, Samo; Stöttinger, Yvonne; Strauch, Steffen; Thiel, Michaela; Tyukin, Alexey; Weber, Adrian; Yaron, Israel
Source
Subject
Language
Abstract
We present measurements of the electron helicity asymmetry in quasi-elastic proton knockout from $^{2}$H and $^{12}$C nuclei by polarized electrons. This asymmetry depends on the fifth structure function, is antisymmetric with respect to the scattering plane, and vanishes in the absence of final-state interactions, and thus it provides a sensitive tool for their study. Our kinematics cover the full range in off-coplanarity angle $\phi_{pq}$, with a polar angle $\theta_{pq}$ coverage up to about 8 degrees. The missing energy resolution enabled us to determine the asymmetries for knock-out resulting in different states of the residual $^{11}$B system. We find that the helicity asymmetry for $p$-shell knockout from $^{12}$C depends on the final state of the residual system and is relatively large (up to $\approx 0.16$), especially at low missing momentum. It is considerably smaller (up to $\approx 0.01$) for $s$-shell knockout from both $^{12}$C and $^2$H. The data for $^2$H are in very good agreement with theoretical calculations, while the predictions for $^{12}$C exhibit differences with respect to the data.