CDC run 2551 drift time fits

Fit function: 
  TF1 *g2 = new TF1("g2","[0] * (1 + [1]*exp(([3]-x)/[2]) + [7]*exp(([3]-x)/[8]) ) / ( (1+exp(([3]-x)/[5])) * (1+exp((x-[4])/[6])) )");

  [0] overall height
  [1] amplitude of 1st exp contrib to peak
  [2] first exp fall-off
  [3] t0
  [4] tmax
  [5] slope up of t0 edge
  [6] slope down of tmax edge
  [7] amplitude of 2nd exp contrib to peak
  [8] second exp fall-off

Drift time fit for straw 496

Drift time fit for straw 500

Drift time fit function

Drift time fit t0

Drift time fit tmax

Drift time fit tmax vs parameter 6

Drift time fit tmax vs parameter 8

Drift time fit parameter 6 vs parameter 8