Bichsel I70m Values give the proper means with saturation corrections at low mT-mo to within 2%. The high γβ dependence in the relativistic rise has already been studied: http://arxiv.org/pdf/0807.4303. However, in order to take our spectra further, we must study the low momentum dependence of the dE/dx variation.
It is expected that detector readout and electronics effects should change the theoretical Bichsel values. Furthermore It was found that this change was dependent upon particle multiplicity in the TPC and was different for π vs K,p and e. The low momentum was not fit as a saturation correction has been applied to this region.
Shown below is the variation in means as a funciton of global momentum (things change slightly in primary momentum or mT-mo due to incorrect momentum correction for electrons, etc.) Below the left plot shows the variation for dE/dx of global tracks in momentum as a function of mean refmult (used to understand dE/dx dependence). The right plot shows the variation of dE/dx of primary tracks in mT-mo as a function of mean refmult (used in analysis).
The dependence is fit for each particle using either a pol1 or pol2 fit. We use this dependence to find the proper location of the means in particle spectra extraction: Spectra Fits