Slopefit is a free, fast, easily scriptable, command line program for fitting functions to particle momentum spectra.
The transverse momentum distribution of particles created in heavy ion collisions can be fitted with the following expression:
dN
mTdmT = A (mT/m)alpha exp(-mT/T) where A, alpha and T are the fitted parameters. T is a temperature-like quantity, called the inverse slope parameter.
Slopefit fits three parameters by default, but you can fix alpha or T with the command line options -a and -t. The format of the input datafile can be specified with the -F option, but the program recognizes some predefined formats also from the extension of the input file. The input file may contain the standard deviations s of the data (last column). In that case, the standard deviations of the fitted parameters will be correct. If there is a y (rapidity) column (first column) in the input file, the program fits the data independently for each y value. You can get detailed help by typing "slopefit -h".