Results from the Particle Tracking System of the Qweak Experiment

The goal of the Qweak experiment is to measure the value of the weak charge of the proton, $Q^{p}_{weak}=1-4\sin^2\theta_{w}$, to 4\% precision. Because the Standard Model makes a firm prediction of $Q^{p}_{weak}$, the measurement of $Q^{p}_{weak}$ will either confirm the prediction or will provide clear evidence for new physics. In this experiment, we study elastic electron proton scattering at four momentum transfer $Q^2$=0.03GeV$^2/$c$^2$ by scattering a high current polarized electron beam on a liquid hydrogen target. A crucial element to the precise measurement of $Q^{p}_{weak}$ is to determine the four momentum transfer $Q^2$ to a high precision because the parity violation asymmetry is directly proportional to $Q^2$: $A^p_{LR}=A_0[Q^p_{weak}Q^2+B_4(Q^2)Q^4+...]$. Therefore, the experiment is also designed to run in a low current mode in which the $Q^2$ is determined by using the tracking detectors. The tracking system is aimed at reconstructing the track of a particle to get the $Q^2$ with an accuracy of 1\%. The experiment is now in the phase I data production run, which will end in May 2011. I will describe the procedure of the track reconstruction and the first results coming from it.