Special date because of Fysica 2011
Monday 11 April 2011, 11:00h, at Nikhef in H331
Speaker: Kees de Jager (Jefferson Lab/University of Virginia)
Title: Parity-violating Electron Scattering
Abstract:
The ever-improving quality of the polarized electron beam at Jefferson Lab has made it possible to implement a broad research program of parity-violating electron scattering. In the first decade of JLab operations the focus was on measurements of the contributions from the strange quarks to the electric and charge form factors of the nucleon. With the contribution from the polarized beam to the systematic error on the parity-violating asymmetry now reduced to below the ppb level, the research program has been expanded to include measurements of the neutron distribution in heavy nuclei and low-energy tests of the Standard Model. Parity violation in deep-inelastic scattering can provide accurate results for the axial-vector electron-quark coupling constant C_2^{u,d}. An initial experiment has just been successfully completed, but a full study has been approved with the 12 GeV upgrade, reusing one of the large solenoids that will become available in the next few years. The broad range of kinematics that such a solenoid will allow to cover, will make it possible to extract separately possible contributions from charge-symmetry violation and higher-twist effects. Another approved experiment with the 12 GeV upgrade will study Møller scattering to yield a measurement of the weak coupling constant sin2 theta_W with an accuracy of 0.0003, comparable to that of the existing results from two collider experiments.
link to colloquia pagina