Is the "RG-invariant EFT'' for few-nucleon systems cutoff independent?

TL;DR

This paper critically examines the claim that a certain renormalization group invariant formulation of chiral effective field theory for nucleon-nucleon scattering is cutoff independent, finding limitations beyond leading order.

Contribution

It demonstrates that the RG-invariant EFT framework cannot generally achieve cutoff independence beyond leading order in the $^3P_0$ partial wave.

Findings

Cutoff independence fails beyond leading order in the $^3P_0$ wave.

Previous studies claiming invariance are critically reviewed and found limited.

The framework's assumptions are challenged with detailed analysis.

Abstract

We consider nucleon-nucleon scattering using the formulation of chiral effective field theory which is claimed to be renormalization group invariant. The cornerstone of this framework is the existence of a well-defined infinite-cutoff limit for the scattering amplitude at each order of the expansion, which should not depend on a particular regulator form. Focusing on the $^3P_0$ partial wave as a representative example, we show that this requirement can in general not be fulfilled beyond the leading order, in spite of the perturbative treatment of subleading contributions to the amplitude. Several previous studies along these lines, including the next-to-leading order calculation by Long and Yang [Phys. Rev. C84, 057001 (2011)] and a toy model example with singular long-range potentials by Long and van Kolck [Annals Phys. 323, 1304-1323 (2008)], are critically reviewed and scrutinized in detail.