17-24 July 2013
KTH and Stockholm University Campus
Europe/Stockholm timezone

The QWeak Experiment: A measurement of the proton weak charge and up-down quark weak couplings.

20 Jul 2013, 09:20
F2 (KTH Campus)


KTH Campus

Talk presentation Top and Electroweak Physics Top and Electroweak Physics


Michael Gericke (University of Manitoba)


The Qweak collaboration recently completed a two year long program of measurements, with the aim of making a precision measurement of the parity violating analyzing power from elastic scattering of 1.16 GeV, longitudinally polarized, electrons on protons at low momentum transfer $Q^2 = 0.025~\rm{GeV/c^2}$. At low momentum transfer, the measured asymmetry is directly related to the weak charge of the proton. The Standard Model makes a firm prediction for the size of the weak charge, based on the “running” of the weak mixing angle. Qweak constitutes the first precision measurement of this quantity and provides a test for physics beyond the Standard Model, at a mass scale of about 2 TeV, for the full data set. While most of the data is still being analyzed, I will present the results obtained from about 4% of the data, giving $A_{PV} = -278.8 \pm 34.8 ~\rm{(statistics)} \pm 29.4~\rm{(systematic)}$ ppb. When this result is combined with the other available parity violation measurements at low momentum transfer (atomic and parity violating electron scattering), signifcant new constraints on the weak charges of the up and down quarks are extracted. I will provide an overview of the theory, the experiment, and will discuss the expected results with the full data set.

Primary author

Michael Gericke (University of Manitoba)

Presentation Materials