r the lowest-<i>pT</i> system in an event with <i>n</i> 
systems becomes <i>1 - (1 - P)^(n-1)</i>. Once the fate of the 
lowest-<i>pT</i> system has been decided, the second-lowest is considered
with respect to the ones above it, then the third-lowest, and so on.  

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Once it has been decided which systems should be joined, the actual merging
is carried out in the opposite direction. That is, first the hardest
system is studied, and all colour dipoles in it are found (including to 
the beam remnants, as 