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Among experiments looking for strangeness in nuclear systems, electron scattering Parity-Violation (PV) type experiments aim mainly at measuring the strange quark contributions to the form factors of the proton. They can be accessed by measuring the asymmetry in longitudinally polarized electron elastic scattering. The PV asymmetry is measured at the 10-7 level of accuracy, and when combined with the electromagnetic form factors of the nucleon, the strange form factors can be determined. The full separation of form factors according to quark flavour requires measurements at forward angles on hydrogen and at backward angles on hydrogen and deuterium. The experimental setup used for G0 in the two different configurations is described. The status of the analysis and the current results are presented and discussed in relation with other ex...
Les programmes expérimentaux auprès du S.C. d'Orsay ont commencé il y a un an environ. L'accélérateur est une machine stable mais présentant quelques défauts de jeunesse. De nombreuses voies de recherches amorcées avec un certain succès sont décrites ci-dessous.
The general principle is presented. The application to the G0 experiment [1] was enabled by the specificity of the time encoding ASIC component. On the poster, some encountered difficulties are exposed, together with a possible software remedy. An internal report is in preparation [2]
The analysis of the JLab proton polarization data on the ratio µpGEp(t)/GMp(t) in the framework of the unitary and analytic model of nucleon electromagnetic structure implicates surprising nondipole behavior of the proton electric form factor GEp(t) in the space-like region with the zero around the momentum transfer squared value t=-Q2=-13 GeV2. This result differs from the unpolarized cross-section measurements giving the dipole behavior of GEp(t) by means of the Rosenbluth technique. Recent investigations demonstrate that inclusion of a two-photon mechanism could solve the problem, which plays an important role for the unpolarized cross section, but it is negligible for the polarization ratio. Here, investigating a size of a difference in a prediction of the deuteron elastic structure functions A(t),B(t) by both, the nondipole and th...
The first experimental results for coherent $\pi^0$-electroproduction on the deuteron, $e+d\to e+d +\pi^0$, at large momentum transfer, are reported. The experiment was performed at Jefferson Laboratory at an incident electron energy of 4.05 GeV. A large pion production yield has been observed in a kinematical region for 1.1$
The non-relativistic impulse approximation of deuteron electromagnetic form factors is used to investigate the space-like region behavior of the proton electric form factor in regard of the two contradictory experimental results extracted either from Rosenbluth separation method or from recoil proton JLab polarization data.
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