See the HARP publication http://arxiv.org/abs/0706.1600, the goal is to replicate figure 30 in a simulation.
The graph shows yield of pi+ and pi- integrated over three different regions:
Incident proton momenta used in the graph are 3, 5, 8 and 12 GeV/c.
Simulations were made in MARS for each of these cases with at least 1 million incident protons and the yield of pions integrated over the above ranges. Incoming beam was assumed to be a pencil beam (no spatial or angular spread) with a 1% RMS Gaussian spread in momentum around the nominal value.
Dimensions for the 5% interaction length tantalum target were taken from http://pppa.group.shef.ac.uk/harp/ta5.html. The simulations used a cylinder of length 5.6 mm (nominal) and radius 15.07063 mm (average of measured values).
Proton momentum (GeV/c) | Incident protons simulated | pi+ per proton | pi- per proton | ||||
---|---|---|---|---|---|---|---|
3 | 3.453 × 106 | 0.006589 | 0.00424 | 0.002244 | 0.006466 | 0.003875 | 0.001728 |
5 | 1 × 106 | 0.015915 | 0.011591 | 0.005759 | 0.016632 | 0.011557 | 0.005354 |
8 | 1 × 106 | 0.024146 | 0.018304 | 0.0089 | 0.025517 | 0.018929 | 0.009239 |
12 | 1 × 106 | 0.027387 | 0.020883 | 0.010101 | 0.030978 | 0.022904 | 0.01094 |
Note that the three integration regions are listed left-to-right in decreasing order of size in these tables. In figure 1 it should be clear which are which, as with the graph it is based on.
Proton momentum (GeV/c) | pi+ per proton.GeV | pi- per proton.GeV | ||||
---|---|---|---|---|---|---|
3 | 0.002988 | 0.001923 | 0.001018 | 0.002933 | 0.001757 | 0.000783 |
5 | 0.003836 | 0.002794 | 0.001388 | 0.004009 | 0.002785 | 0.00129 |
8 | 0.003393 | 0.002572 | 0.001251 | 0.003586 | 0.00266 | 0.001298 |
12 | 0.002468 | 0.001882 | 0.00091 | 0.002791 | 0.002064 | 0.000986 |
I suspect the "arbitrary units" in the HARP publication's figure 30 are in fact units of 10-4 of the ones used here. It would be helpful to compare the absolute numbers here if they are available.