The Q(weak)(p) experiment: A test for physics beyond the standard model via a precision measurement of the proton weak charge

The Qweak collaboration is currently preparing a measurement of the proton's weak charge Qwp align=middle/ = (1 < 4 sin2 w) at the Thomas Jefferson National Accelerator Facility (TJNAF). The experiment has been designed to produce a 4.1% measuremen t of the weak charge, via a 2.5% measurement of the parity violating asymmetry in the number of elastically scattered 1 GeV electrons from protons, at forward angles. At the proposed precision, the experiment would produce a 0.3% measurement of the weak m ixing angle at a momentum transfer of 0.16 GeV, making it the most precise stand alone measurement of the weak mixing angle at low momentum transfer. In combination with other parity measurements, Qweak will also provide a high precision determination of the weak charges of the up and down quarks. Our proposed measurement of Qw2 align=middle/ will be performed with significantly smaller statistical and systematic errors than existing low Q2 data. Any significant deviation from the Standard Model predictio n at low momentum transfer (Q2) would be a signal of new physics, whereas agreement would place new and significant constraints on possible Standard Model extensions. The experiment is currently being prepared for installation, beginning in late 2009, and data taking beginning in mid 2010.

25.30.Bf
14.80.Bn
11.30.Er
parity
electron-electron scattering
standard model

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