dorsal/arxiv
View SchemaThe $p p \to p p\pi^0$ Reaction near Threshold: A Chiral Power Counting Approach
| Authors | T. D. Cohen, J. L. Friar, G. A. Miller, U. van Kolck |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9512036 |
| URL | https://arxiv.org/abs/nucl-th/9512036 |
| DOI | 10.1103/PhysRevC.53.2661 |
| Journal | Phys.Rev.C53:2661-2673,1996 |
Abstract
We use power-counting arguments as an organizing principle to apply chiral perturbation theory, including an explicit $\Delta$, to the $p p \rightarrow p p \pi^0$ reaction near threshold. There are two lowest-order leading mechanisms expected to contribute to the amplitude with similar magnitudes: an impulse term, and a $\Delta$-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 $\Delta$-excitation terms. In addition, we have modeled the short-ranged interaction using $\sigma$ and $\omega$ 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.
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"abstract": "We use power-counting arguments as an organizing principle to apply chiral\nperturbation theory, including an explicit $\\Delta$, to the $p p \\rightarrow p\np \\pi^0$ reaction near threshold. There are two lowest-order leading mechanisms\nexpected to contribute to the amplitude with similar magnitudes: an impulse\nterm, and a $\\Delta$-excitation mechanism. We examine formally sub-leading but\npotentially large mechanisms, including pion-rescattering and short-ranged\ncontributions. We show that the pion-rescattering contribution is enhanced by\noff-shell effects and has a sign opposite to that of a recent estimate based on\na PCAC pion interpolating field. Our result is that the impulse term interferes\ndestructively with the pion rescattering and $\\Delta$-excitation terms. In\naddition, we have modeled the short-ranged interaction using $\\sigma$ and\n$\\omega$ exchange mechanisms. A recoil correction to the impulse approximation\nis small. The total amplitude obtained including all of these processes is\nfound to yield cross sections substantially smaller than the measured ones.",
"arxiv_id": "nucl-th/9512036",
"authors": [
"T. D. Cohen",
"J. L. Friar",
"G. A. Miller",
"U. van Kolck"
],
"categories": [
"nucl-th"
],
"doi": "10.1103/PhysRevC.53.2661",
"journal_ref": "Phys.Rev.C53:2661-2673,1996",
"title": "The $p p \\to p p\\pi^0$ Reaction near Threshold: A Chiral Power Counting Approach",
"url": "https://arxiv.org/abs/nucl-th/9512036"
},
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