Parameterization of deflections/preliminary momentum resolution results

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Using the 1500 Amp TOSCA map provided by Paul Brindza, I ran Garfield calculations over a grid in z and r corresponding to the dimensions of the FDC to compute the deflections of the avalanches along the wire due to the Lorentz force. The behavior of this deflection for ionizations throughout a given FDC cell is well-described by a plane (the example below is for B=+2.0 T along the beam line):

Deflection example.gif

The two slope (tangent) parameters describing the deflection planes are shown as a function of r and z(beam direction) here:

Tan def angles.gif

The hitFDC.c routine in HDGeant has been modified to read in a table of these tangent values and interpolate the amount of deflection as a function of the point of closest approach to the avalanche wire on a wire-by-wire/event-by-event basis.