The efficiency corrections to the spectra were done with a matrix to account not only for the loss of particle, but also sytematic shifting of the particles in momentum.  The idea is that a 2-D matrix is generated with one index as the input moentum, and the other index is the found momentum.  A normilization and inversion of this matrix provides a method to correct the spectra for both loss and shifting of the momentum.  A detailed discription of this method was outlined in Draper's e-mail of 17July2000.