S. Kegel

S. Kegel
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S. Kegel

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Nuclear Experiment (2)
High Energy Physics - Experiment (2)
Physics - Instrumentation and Detectors (1)
Physics - Accelerator Physics (1)

Publications Authored By S. Kegel

We report on a new experimental method based on initial-state radiation (ISR) in e-p scattering, in which the radiative tail of the elastic e-p peak contains information on the proton charge form factor ($G_E^p$) at extremely small $Q^2$. The ISR technique was validated in a dedicated experiment using the spectrometers of the A1-Collaboration at the Mainz Microtron (MAMI). This provided first measurements of $G_E^p$ for $0. Read More

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. Read More

A massive, but light abelian U(1) gauge boson is a well motivated possible signature of physics beyond the Standard Model of particle physics. In this paper, the search for the signal of such a U(1) gauge boson in electron-positron pair-production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron (MAMI) is described. Exclusion limits in the mass range of 40 MeV up to 300 MeV with a sensitivity in the mixing parameter of down to $\epsilon^2 = 8\times 10^{-7}$ are presented. Read More