Two-pion-exchange effects in the $pp\to pp\pi^0$ reaction

TL;DR

This paper investigates the near-threshold pp → ppπ^0 reaction using heavy-baryon chiral perturbation theory, revealing that two-pion-exchange diagrams dominate over one-pion-exchange contributions, challenging traditional counting schemes.

Contribution

It demonstrates the significant role of two-pion-exchange diagrams in the reaction, providing new insights into chiral perturbation theory applications in nuclear reactions.

Findings

Two-pion-exchange diagrams dominate near threshold.

One-pion-exchange is of lower chiral order but less significant.

Results challenge traditional Weinberg counting scheme.

Abstract

We study the pp \to pp\pi^0 reaction near threshold based on heavy-baryon chiral perturbation theory. We show that the two-pion-exchange diagrams give much larger contribution than the one-pion-exchange diagram which is of lower chiral order in Weinberg's counting scheme. We also discuss the relation of our results to the momentum counting scheme.