G ⁰

A central focus of our research is a program of precision experiments that use parity-violating electron scattering to probe the structure of nucleons (proton, neutron). Parity violation arises due to the quantum interference between photon exchange (electromagnetic) and Z ⁰ -exchange (neutral-current weak) processes.

The G ⁰ experiment is sensitive in particular to the contributions of strange quarks (a component of the sea of virtual quark-antiquark pairs) to the electromagnetic structure of the nucleon. The G ⁰ experiment measure the parity-violating asymmetry from elastic electron scattering on the proton at both forward and backward angles over a range of momentum transfers from 0.1 to 1.0 GeV ² . This will allow ultimately a `Rosenbluth-type' separation of the magnetic and electric form factors arising from strange quarks. Quasi-elastic scattering from a deuterium target will also be used to provide access to the axial vector form factor (and hence the nucleon anapole moment). Inelastic scattering events will access the neutral weak N-Delta form factor. More detailed information on G ⁰ can be found here .

The forward angle data results have been published in 2005. The data taking for the backward angle ended in March 2007.  

Our group has been part of the project since 1999. We have worked on detector devellopement, data acquisition and data analysis. More informations on J. Roche's involvement can be found here , more informations on P. King's involvement can be found here . Our group is taking part to the analysis of the backward angle data with a specific focus on the transverse electron polarization data.

Publications resulting from this work: here .