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HK: Fachverband Hadronen und Kerne
HK 80: Hadron Structure and Spectroscopy I
HK 80.7: Talk
Friday, March 20, 2009, 12:30–12:45, H-ZO 20
The Qweak experiment - A search for new physics at the TeV scale — •Klaus Grimm — Louisiana Tech University, Ruston, LA 71272, USA
The Qweak experiment is a new precision measurement of the weak charge of the proton, QpW=1−4sin2(θW), using parity violation in electron scattering from the proton at very low Q2 and forward angles and is in the final stages of preparation for execution at Jefferson Laboratory (JLab). The Standard Model makes a firm prediction of QpW, based on the running of the weak mixing angle sin2(θW) from the Z0 pole down to lower energies. Because the electroweak radiative corrections which give rise to the running depend not only on known particles, but on particles which have not yet been discovered, a difference between the calculated and measured weak charges may signal new physics where Qweak will be sensitive to new physics at the few TeV scale. Any significant deviation of sin2(θW) from the Standard Model prediction at low Q2 would be a signal of new physics, where as agreement would place new and strict constraints on possible Standard Model extensions. In the absence of new physics Qweak will provide a 0.3% determination of sin2(θW), making this a very competitive stand-alone measurement of the weak mixing angle indeed.
The experiment plans to measure the predicted parity violating asymmetry of -0.3 ppm with a combined statistical and systematic uncertainty of 2.2%, corresponding to a total uncertainty of 4% in QpW.