5 research outputs found
Coherent \pi^0 threshold production from the deuteron at Q^2 = 0.1 GeV^2/c^2
First data on coherent threshold \pi^0 electroproduction from the deuteron
taken by the A1 Collaboration at the Mainz Microtron MAMI are presented. At a
four-momentum transfer of q^2=-0.1 GeV^2/c^2 the full solid angle was covered
up to a center-of-mass energy of 4 MeV above threshold. By means of a
Rosenbluth separation the longitudinal threshold s wave multipole and an upper
limit for the transverse threshold s wave multipole could be extracted and
compared to predictions of Heavy Baryon Chiral Perturbation Theory.Comment: 7 pages, 7 figures, latex2
The horizontal drift chambers for the focal plane proton-polarimeter of the 3-spectrometer setup at MAMI
Large-area horizontal drift chambers have been built for use in a proton polarimeter. A gas mixture of 20% argon and 80% ethane is used. The left–right assignment is achieved by measuring the difference of the signals induced on neighboring potential wires. A spatial resolution of 300 μm is achieved
The focal plane proton-polarimeter for the 3-spectrometer setup at MAMI
For (e- gt ,e prime p- gt ) experiments the 3-spectrometer setup of the A1 collaboration at MAMI has been supplemented by a focal plane proton-polarimeter. To this end, a carbon analyzer of variable thickness and two double-planes of horizontal drift chambers have been added to the standard detector system of Spectrometer A. Due to the spin precession in the spectrometer magnets, all three polarization components at the target can be measured simultaneously. The performance of the polarimeter has been studied using elastic p(e- gt ,e prime p- gt ) scattering
Neutral pion threshold production at Q<sup>2</sup>=0.05 GeV<sup>2</sup>/c<sup>2</sup> and chiral perturbation theory
New data are presented on the p (e, e'p)pi(o) reaction at threshold at a four-momentum transfer of Q<sup>2</sup>=0.05 GeV<sup>2</sup>/c<sup>2</sup> The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAML The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions