The Qweak tracking system

Measurement of the average Q2 and the dilution by background events
  • Klaus H. Grimm
Conference paper


The Q weak P 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 8° ± 2°, corresponding to Q2 ∼ 0.03 (GeV/c)2, on eight Čerenkov 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 Čerenkov detectors, and for the dilution of the Čerenkov detector signal by background.


Focal Plane Tracking System Interaction Vertex Drift Chamber Toroidal Magnetic Field 
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  1. 1.
    Qweak Collaboration, R. Carlini et al.: Jefferson Lab Proposal E-02-020, available at: Scholar
  2. 2.
    See G.R. Smith, in these proceedings, Qweak: A Precision Measurement of the Proton’s Weak ChargeGoogle Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Klaus H. Grimm
    • 1
  1. 1.The College of William & MaryWilliamsburgUSA

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