The pp → ppπ Reaction near Threshold: A Chiral Power Counting Approach


We use power-counting arguments as an organizing principle to apply chiral perturbation theory, including an explicit ∆, to the pp → ppπ0 reaction near threshold. There are two lowest-order leading mechanisms expected to contribute to the amplitude with similar magnitudes: an impulse term, and a ∆-excitation mechanism. We examine formally sub-leading but potentially large mechanisms, including pion-rescattering and short-ranged contributions. We show that the pion-rescattering contribution is enhanced by off-shell effects and has a sign opposite to that of a recent estimate based on a PCAC pion interpolating field. Our result is that the impulse term interferes destructively with the pion rescattering and ∆-excitation terms. In addition, we have modeled the short-ranged interaction using σ and ω exchange mechanisms. A recoil correction to the impulse approximation is small. The total amplitude obtained including all of these processes is found to yield cross sections substantially smaller than the measured ones. DOE/ER/40427-26-N95 DOE/ER/40762-074, U of MD pp 96-058

Cite this paper

@inproceedings{Cohen1996TheP, title={The pp → ppπ Reaction near Threshold: A Chiral Power Counting Approach}, author={Thomas Cohen and James L. Friar and Gerald A. Miller and Ubirajara van Kolck}, year={1996} }