dorsal/arxiv
View SchemaNucleon-Nucleon Effective Field Theory at NNLO: Radiation Pions and 1S0 Phase Shift
| Authors | Thomas Mehen, Iain W. Stewart |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9906010 |
| URL | https://arxiv.org/abs/nucl-th/9906010 |
Abstract
Low energy phenomena involving two nucleons can be successfully described using effective field theory. Because of the relatively large expansion parameter, it is only at next-to-next-to-leading order (NNLO) where one can expect to see agreement with experiment at the few percent level. The first part of this talk will focus on radiation pion effects, which first appear at NNLO. The power counting for radiation pions is simple for center of mass momentum p~\sqrt{M m_pi}=Q_r, the threshold for pion production. We explain how graphs calculated with the Q_r power counting scale for p~m_\pi. The Q_r^3 radiation pion contributions to nucleon-nucleon scattering are suppressed by inverse powers of the S-wave scattering lengths. However, we point out that order Q_r^4 radiation contributions might give a NNLO contribution for p~m_pi. In the second part of the talk, results for the potential pion and contact interaction part of the NNLO 1S0 phase shift are presented. We emphasize the importance of eliminating spurious poles in the expression for the amplitude at each order in the perturbative expansion. Doing this leaves a total of three free parameters at NNLO. We obtain a good fit to the 1S0 phase shift.
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"abstract": "Low energy phenomena involving two nucleons can be successfully described\nusing effective field theory. Because of the relatively large expansion\nparameter, it is only at next-to-next-to-leading order (NNLO) where one can\nexpect to see agreement with experiment at the few percent level. The first\npart of this talk will focus on radiation pion effects, which first appear at\nNNLO. The power counting for radiation pions is simple for center of mass\nmomentum p~\\sqrt{M m_pi}=Q_r, the threshold for pion production. We explain how\ngraphs calculated with the Q_r power counting scale for p~m_\\pi. The Q_r^3\nradiation pion contributions to nucleon-nucleon scattering are suppressed by\ninverse powers of the S-wave scattering lengths. However, we point out that\norder Q_r^4 radiation contributions might give a NNLO contribution for p~m_pi.\nIn the second part of the talk, results for the potential pion and contact\ninteraction part of the NNLO 1S0 phase shift are presented. We emphasize the\nimportance of eliminating spurious poles in the expression for the amplitude at\neach order in the perturbative expansion. Doing this leaves a total of three\nfree parameters at NNLO. We obtain a good fit to the 1S0 phase shift.",
"arxiv_id": "nucl-th/9906010",
"authors": [
"Thomas Mehen",
"Iain W. Stewart"
],
"categories": [
"nucl-th",
"hep-ph"
],
"title": "Nucleon-Nucleon Effective Field Theory at NNLO: Radiation Pions and 1S0 Phase Shift",
"url": "https://arxiv.org/abs/nucl-th/9906010"
},
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