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In the absence of screening, bmaxlbmin ~ (hq)IE' x Mclh = EIE'. 3 Bremsstrahlung 29 Next apply this to bremsstrahlung. 4a. In principle, either the electron or nucleus could be taken as the incident particle depending on t he reference frame used. The Weizsacker- Williams method evaluated in the laboratory considers the field of the incident electron as a set of virtual photons, which are then Compton scattered by the nucleus. Call this process one. The same method used in a fr ame in which the electron is at rest considers t he field of the nucleus as the set of virtual photons.

For the simplest approximation, the function F is given by r; E - E' [ F = -E- T where T T + 1/18 (E - E' -E- +E 2) + 49" 4T +12/9 ]' E - E' - 3" = In(183Z- 1 / 3 ). 5 Bremsstrahlung: N(photons) versus E(photons). material, thus destroying the coherence of the state. For electron energies in the Te V range, this effect starts to become significant in describing their energy losses. For electrons of 100 GeV or lower, only the very-low-energy part of the spectrum is strongly affected. Very roughly, the effect is large for E'/E < 4 x 1O- 5 E(GeV)/Xo(cm).

Dead times are typically 200 r ns . The resolution, if only a single wire is hit, is (J = anode spacing/ J12. Drift chambers are a different modification of a PWC. 8d). The drift velocity for electron is then constant for most of the electron path. For constant drift velocity? the time at which a signal arrives at the wire measures the distance fro lr the wire at which the particle passed through the detector. Drift distance ~ range up to 10 cm or so. A typical drift chamber will have many signa wires.