0000000000281843
AUTHOR
H. J. Kreidel
Beam-normal single spin asymmetry in elastic electron scattering off 28Si and 90Zr
We report on a new measurement of the beam-normal single spin asymmetry $A_{\mathrm{n}}$ in the elastic scattering of 570 MeV transversely polarized electrons off $^{28}$Si and $^{90}$Zr at $Q^{2}=0.04\, \mathrm{GeV}^2/c^2$. The studied kinematics allow for a comprehensive comparison with former results on $^{12}$C. No significant mass dependence of the beam-normal single spin asymmetry is observed in the mass regime from $^{12}$C to $^{90}$Zr.
Vertical Beam Polarization at MAMI
For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymmetry $A_{\mathrm{n}}$, which is a direct probe of higher-order photon exchange beyond the first Born approximation, has been measured in the reaction $^{12}\mathrm C(\vec e,e')^{12}\mathrm C$. Vertical polarization orientation was necessary to measure this asymmetry with the existing experimental setup. In this paper we describe the procedure to orient the electron polarization vector vertically, and the concept of determining both its magnitude and orientation with the available setup. A sophisticated method has …
Present state of the MAMI control system
Abstract MAMI (Mainz Microtron) is an electron accelerator consisting of a cascade of three race-track microtrons, with an output electron beam of 855 MeV and 100 μA cw [1]. The first two stages (output energy 180 MeV) were operative for nuclear-physics experiments from 1983 to 1987 and have since been transferred to a new building. They will serve as an injector for the third stage, now under construction. The control system for MAMI was based on a versatile process communication software system for a network of processors with multiprocess operating systems. This system has previously proved very successful, so we decided to rely on it as control system for the new, upgraded accelerator, …
First Measurement of the $Q^2$ Dependence of the Beam-Normal Single Spin Asymmetry for Elastic Scattering off Carbon
We report on the first Q^{2}-dependent measurement of the beam-normal single spin asymmetry A_{n} in the elastic scattering of 570 MeV vertically polarized electrons off ^{12}C. We cover the Q^{2} range between 0.02 and 0.05 GeV^{2}/c^{2} and determine A_{n} at four different Q^{2} values. The experimental results are compared to a theoretical calculation that relates A_{n} to the imaginary part of the two-photon exchange amplitude. The result emphasizes that the Q^{2} behavior of A_{n} given by the ratio of the Compton to charge form factors cannot be treated independently of the target nucleus.