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We use power-counting arguments as an organizing principle to apply chiralperturbation theory, including an explicit $\Delta$, to the $p p \rightarrow pp \pi^0$ reaction near threshold. There are two lowest-order leading mechanismsexpected to contribute to the amplitude with similar magnitudes: an impulseterm, and a $\Delta$-excitation mechanism. We examine formally sub-leading butpotentially large mechanisms, including pion-rescattering and short-rangedcontributions. We show that the pion-rescattering contribution is enhanced byoff-shell effects and has a sign opposite to that of a recent estimate based ona PCAC pion interpolating field. Our result is that the impulse term interferesdestructively with the pion rescattering and $\Delta$-excitation terms. Inaddition, we have modeled the short-ranged interaction using $\sigma$ and$\omega$ exchange mechanisms. A recoil correction to the impulse approximationis small. The total amplitude obtained including all of these processes isfound to yield cross sections substantially smaller than the measured ones.Comment: 39 pages, latex, 16 figures, omega pair exchange added, published  versio

physical review. c. nuclear physics/physical review. c, nuclear physics

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>pp</mml:mi><mml:mo>→</mml:mo><mml:mi>pp</mml:mi><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>reaction near threshold: A chiral power counting approach

pp→ppπ0reaction near threshold: A chiral power counting approach