# The Two-Nucleon 1S0 Amplitude Zero in Chiral Effective Field Theory

## TL;DR

This paper develops a new rearrangement of short-range interactions in the $^1S_0$ nucleon-nucleon channel within Chiral Effective Field Theory, accurately reproducing the amplitude zero and fitting empirical phase shifts up to the pion-production threshold.

## Contribution

It introduces a novel rearrangement scheme that captures the amplitude zero at leading order and achieves systematic improvements at next-to-leading order within Chiral EFT.

## Key findings

- Successfully reproduces the amplitude zero at ~340 MeV
- Achieves excellent fit to empirical phase shifts up to pion-production threshold
- Provides analytic results in a pionless approach that match phenomenology well

## Abstract

We present a new rearrangement of short-range interactions in the $^1S_0$ nucleon-nucleon channel within Chiral Effective Field Theory. This is intended to reproduce the amplitude zero (scattering momentum $\simeq$ 340 MeV) at leading order, and it includes subleading corrections perturbatively in a way that is consistent with renormalization-group invariance. Systematic improvement is shown at next-to-leading order, and we obtain results that fit empirical phase shifts remarkably well all the way up to the pion-production threshold. An approach in which pions have been integrated out is included, which allows us to derive analytic results that also fit phenomenology surprisingly well.