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

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Ohio University will design and build two sets of triggerscintillators for the Qweak experiment at Jefferson Lab. Thisimportant new experiment will measure the weak charge of the proton,as a precision test of the running of the weak mixing angle, thusproviding a uniquely sensitive probe of physics beyond the StandardModel of particle physics. The trigger scintillators are an essential component of the Qweakparticle tracking system, and will be used to start the electronicsand to veto neutral particles during the calibration and backgroundmeasurements. Each scintillator will be 225 cm x 16 cm x 1 cm andmade from BC408 or its equivalent. Non-UVT lightguides at each endwill provide a mechanically reliable optical coupling joint. UVT rodsthat are 5.1 cm in diameter and 5 cm long will couple the rectangularlightguide to the photomultiplier tubes. The long edges of thescintillators will be diamond milled and the ends finished to a 600grit sanded finish. Given the extreme ratio of thickness to length,the scintillator counters must be supported by a frame which is thenmountable to the rear chamber package. To reduce radiation damage,this package will be removed from direct view of the beam for the highcurrent running mode. The assembly and testing of the detectors will be done at the OhioUniversity Institute for Nuclear and Particle Physics by a graduatestudent and at least one undergraduate student, under the supervisionof Professor Opper. The Ohio University group will also develop the fast triggering system which is required for this experiment. When the detectors have been deemed ready for installation, the students will participate in their commissioning at Jefferson Lab.