The Qweak tracking system
Measurement of the average Q2 and the dilution by background eventsKlaus H. Grimm
The College of William & Mary, Department of Physics, Williamsburg, VA 23187-8795, USA
(Received 01 November 2004 / Published online 08 February 2005)
The Qweakp experiment will measure the parity-violating elastic e-p scattering asymmetry to extract the weak charge of the proton. The experiment employs a toroidal magnet to focus electrons scattered at 8o ± 2o, corresponding to Q2 ~ 0.03 (GeV/c)2, on eight Cerenkov detectors located in the focal plane of the spectrometer. Since the asymmetry is proportional to Q2, it is crucial to obtain an accurate measure of the acceptance-averaged value of Q2. A tracking system will be used in a low-rate counting mode, allowing individual events to be observed. This will enable a determination of the average Q2 by measuring the scattering angle and interaction vertex, for mapping the response across the surface of the Cerenkov detectors, and for the dilution of the Cerenkov detector signal by background.
PACS: 25.30.Bf Elastic electron scattering - 29.40.Gx Tracking and position-sensitive detectors
The Author, for the Qweak Collaboration
© Società Italiana di Fisica, Springer-Verlag 2005