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:

= 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".


The data file alcor1.txt contains kaon momentum distribution from a Monte Carlo simulation, and it is in .ymtm format. It means that its columns are: y, mT-m, dN/mTdmT, s.
The switch -v means verbose mode, option -m 0.4936 specifies the kaon mass, and .ymtm is needed because the suffix of alcor1.txt is not .ymtm.

dali~/Doc/ slopefit -vm 0.4936 alcor1.txt .ymtm
# m=0.493600
# y     T       alpha   A       s_T     s_alpha s_A     N       chi^2   z
0.000   0.32402 -1.0720 915.849 8.5e-03 7.3e-02 3.2e+01 30      25.9    -0.058
0.250   0.33568 -1.1803 870.670 6.6e-03 5.3e-02 2.2e+01 30      30.5    +0.545
0.500   0.31930 -1.0022 900.806 6.0e-03 5.3e-02 2.3e+01 30      25.0    -0.192
0.750   0.31825 -0.9738 840.232 6.1e-03 5.4e-02 2.2e+01 30      24.5    -0.255
1.000   0.31349 -0.8453 744.147 6.1e-03 5.6e-02 2.0e+01 30      25.7    -0.087
1.250   0.32357 -0.8337 552.138 7.0e-03 6.2e-02 1.6e+01 30      31.3    +0.651
1.500   0.33701 -0.9689 360.404 9.3e-03 7.5e-02 1.2e+01 30      29.2    +0.377
1.750   0.31747 -0.9969 227.319 1.2e-02 1.1e-01 1.1e+01 30      34.9    +1.077
2.000   0.28832 -1.2629 129.133 1.7e-02 1.8e-01 1.2e+01 30      16.4    -1.598
The output columns s_T, s_alpha, s_A are the standard deviations of the fitted parameters, N is the number of data points and z is the Gaussian corresponding to the chi-square.


Source slopefit-1.2.3.tar.gz
Binary RPM for Linux/glibc-2.2 (RedHat 7) slopefit-1.2.3-0.i386.rpm
RPM source slopefit-1.2.3-0.src.rpm

© 1998-2001 Peter Csizmadia