Slopefit

News

• May 27, 2001 Slopefit 1.2.3. More than one datafiles can be processed. New options: --mtmin, --mtmax, --ymin, --ymax
• April 12, 2001 Slopefit 1.2.2. New options: --ptmin and --ptmax
• March 1, 2000 Slopefit 1.2.1, also available as an RPM package
• February 7, 2000 Slopefit 1.2
  Rewrote the program in C++ and implemented 3 new fitting functions:
  • A*m_T*sinh(gamma*v*p_T/T)*T/(gamma*v*p_T)*exp(-gamma*m_T/T)
  • Siemens-Rasmussen formula
  • A*mt*K0(gamma*p_T/T)*I0(gamma*v*p_T/T)

Introduction

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".

Example

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, m_T-m, dN/m_Tdm_T, 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/9705.data/0.16-0.72/outgoing% 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
...

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© 1998-2001 Peter Csizmadia