Collaborative Reseach: Development of a Particle Tracking System for the Qweak Experiment

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Virginia Polytechnic Institute and State University will design andbuild the `Region 2' tracking chambers for the Qweak experiment at Jefferson Lab. This experiment will make a high precision measurement at very low momentum transfer of the proton's weak charge, which is its coupling to the neutral Z boson. A high precision value of the weakmixing angle at low momentum transfer will be extracted, thus providinga sensitive test of the predicted energy scale dependence of this quantityin the electroweak standard model. A failure to observe this expectedbehavior could provide evidence for physics beyond the presently acceptedStandard Model. There are many candidate extensions to the Standard Modelthat would generate observable effects in this experiment. The Region 2 wire chambers are an essential component of the particletracking system, which is needed in order to precisely measure thekinematics of the elastically scattered electrons, as well as forcritical studies of experimental backgrounds. The chambers will consistof two sets of 50 cm x 50 cm horizontal drift chambers. Each drift chamber will have a total of 6 planes of wires. The expected resolutionwill be about 200 microns, providing an angular resolution of 1 mrad. The Region 2 drift chambers will provide quality educational experiencesfor both graduate and undergraduate students. The timescale of the project is well matched to the typical timescale of a graduate student's time in graduate school, so the student will get to participate in all hardware and software phases of the project. The tasks needed to complete the project include design and construction of the chambers, the front-end electronics, and the gas handling system, testing of the finished product, implementation in the Qweak experiment, and data analysis and trackingcode development when the experiment takes data. We expect to involvetwo graduate students and at least two undergraduate students in thiseffort, under the supervision of the faculty and senior research staffat Virginia Tech.