Department of Physics and
Physical Oceanography
Colloquium
“First Results on the Weak Charge of the
Proton – and a Search for Physics Beyond the
Standard Model”
Dr. Allena Opper
Department of Physics, The George Washington University
The weak charge of the proton Qpw is a basic property, which determines the
proton’s response to the weak interaction. The Standard Model predicts the
proton’s weak charge, based on the running of the weak mixing angle, sin2θw from
the Z0 pole to low energies. To challenge those predictions and search for new
physics the JLab Qweak experiment has precisely measured the parity violating
asymmetry in ep elastic scattering, which is proportional to the proton’s weak
charge, Qpw = 1 − 4 sin2 θw, at very low Q2 and forward angles. The predicted
change in sin2θw corresponds to a 10 σ effect in the experiment, thus testing the
internal consistency of the Standard Model more rigorously than complementary
experiments on the weak charge of Cesium (APV) and the electron Qew. This is
the first precision measurement of Qpw, with a combined statistical systematic
uncertainty expected to be ~4%, which will lead to a 0.3% measurement of sin2θw.
The experiment completed its last data taking campaign in May 2012. The results
from the commissioning run will be presented.
Friday, April 19, 2013
2:00 PM
DeLoach Hall, Room 212