Re-emergence of rapidity scale uncertainty in SCET

Understand

The artificial separation of a full-theory mode into distinct collinear and soft modes in SCET leads to divergent integrals over rapidity, which are not present in the full theory.

• Rapidity divergence introduces an additional scale into the problem, giving rise to its own renormalization group with respect to this new scale.
• Two contradicting claims exist in the literature concerning rapidity scale uncertainty.
• One camp has shown that the results of perturbative calculations depend on the precise choice of rapidity scale.