Factorization Doing any calculable predictions would be impossible without simplifications: Break into two stages with very different energy scales: Produce two energetic quarks Hard process as energies are high Very perturbative regime, calculations should work fine Let each quark independently shower (called fragmentation) – difficult: This is much softer process, one would wonder if QCD would even work there At the end of it the groups of quarks/gluons form hadrons (very soft process, perturbative methods can't work – need some modeling) Then apply correction to account for broken strings (add particles between main quarks that are there to cancel the color flow) 3
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