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HOWTO: Print the Pythia event record, and (more importantly) decipher it.

Updated on Wed, 2010-01-06 16:45. Originally created by jwebb on 2010-01-06 16:44.
This blog entry will be a work in progress for a while.  
 
I have setup pythia in starsim and generated an event.  How do I list, in a human-readable format, the particles created?  RTFM pg 51.
 
starsim> trig 1
starsim> call pylist(1)
This will dump the event record.  Depending on the physics setup, you will get output which looks sort of like this--
 

                            Event listing (summary)

    I particle/jet KS     KF  orig    p_x      p_y      p_z       E        m

    1 !p+!         21    2212    0    0.000    0.000  249.998  250.000    0.938
    2 !p+!         21    2212    0    0.000    0.000 -249.998  250.000    0.938
 ============================================================================== [[A]]
    3 !d!          21       1    1   -1.011    1.088   54.655   54.676    0.000
    4 !g!          21      21    2   -1.436   -0.449  -19.737   19.795    0.000
    5 !d!          21       1    3   -0.962    1.035   51.995   52.014    0.000
    6 !ubar!       21      -2    4   -0.160   -7.419   -8.357   11.177    0.000
    7 !W-!         21     -24    0   -1.122   -6.384   43.637   63.191   45.242
    8 !d!          21       1    7    6.883   18.376   20.294   28.231    0.330
    9 !ubar!       21      -2    7   -8.005  -24.760   23.343   34.959    0.330
 ============================================================================== [[B]]
   10 (W-)         11     -24    7   -1.122   -6.384   43.637   63.191   45.242
   11 (u)       A  12       2    4   -1.325    7.023   -8.720   11.279    0.330
   12 (ud_0)    V  11    2101    2    0.943    0.420  -88.074   88.080    0.000
   13 (dbar)    A  12      -1    1    0.168   -0.307   10.600   10.606    0.000
   14 (g)       I  12      21    8    1.075    0.690    1.111    1.693    0.000
   15 (d)       V  11       1    8    8.778   11.758   16.350   21.971    0.330
....
   39 (ubar)    V  11      -2    9   -1.548   -3.735    4.240    5.868    0.330
   40 (ud_0)    A  12    2101    1    0.463   -0.212  137.527  137.528    0.000
   41 (u)       V  11       2    2    0.493    0.029 -142.141  142.142    0.000
 ============================================================================== [[C]]
   42 (string)     11      92   11   -0.382    7.443  -96.793   99.359   21.160
   43 (eta')       11     331   42   -0.881    4.959   -6.304    8.125    0.958
   44 (omega)      11     223   42   -0.134    0.528   -2.573    2.744    0.783
   45 pi0           1     111   42   -0.317    1.449   -2.122    2.593    0.135
   46 pi+           1     211   42    0.365   -0.161   -4.154    4.176    0.140
   47 pi-           1    -211   42    0.001   -0.025   -4.561    4.563    0.140
   48 pi0           1     111   42   -0.570    0.545  -10.754   10.784    0.135
....
  122 pi-           1    -211   85   -0.335    0.457   -4.262    4.302    0.140
  123 pi0           1     111   85    0.379    0.144   -3.761    3.786    0.135
  124 K_L0          1     130   86    0.161   -0.269   -0.779    0.976    0.498
  125 K_L0          1     130   87    0.036   -0.291   -9.870    9.887    0.498
  126 pi+           1     211   88    0.055   -0.061   -6.728    6.730    0.140
  127 pi-           1    -211   88   -0.240    0.112  -11.581   11.585    0.140
  128 pi0           1     111   88    0.169    0.289   -8.308    8.316    0.135
 ============================================================================== [[D]]
                   sum:  2.00        -0.000    0.000   -0.000  500.000  500.000
Pythia was configured to generate pp --> W+ X, and the [[X]] notations are my addition.
 
Above [[A]] we have the two beams.  Below [[D]] we have some summary information.  One can verify that the charge (first column), momenta, mass and energy are all conserved.  These are fairly straightforward to understand.  The rest of the event record requires us to actually read the pythia manual.
 
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