arXiv 1111.49342011-11-21hep-phhep-latnucl-exnucl-th

$πN$散射振幅II的相对论手征表示：π-核子σ项

Relativistic chiral representation of the $πN$ scattering amplitude II: The pion-nucleon sigma term

J. Martin Camalich, J. M. Alarcon, J. A. Oller

备注：: PROCEEDINGS to the 33rd International School of Nuclear Physics "From Quarks and Gluons to Hadrons and Nuclei"-7 pag, 1 fig, 2 tables
DOI：: 10.1016/j.ppnp.2011.12.038

摘要：

本文基于Lorentz协变重子手征微扰理论中$πN$散射振幅的新分析，给出了π介子-核子σ项的确定方法.这个振幅，有效的下一个到下一个领先的手征展开顺序，系统地包括$Δ(1232)$的影响，给出了一个可靠的描述不同的分波分析的相移能量刚好低于共振区。我们得到的一些观测值的实验范围内和现象学的预期预测。特别地，我们使用质心能量依赖的幅度调整与阈值以上的数据，以准确地提取值的$σ_{πN}$。我们的研究表明，包括现代介子工厂和介子原子的数据有利于相对较大的值的σ项。我们报告的值为$σ_{πN}=59(7)$ MeV。

英文摘要：

We present a determination of the pion-nucleon sigma-term based on a novel analysis of the $πN$ scattering amplitude in Lorentz covariant baryon chiral perturbation theory renormalized in the extended-on-mass-shell scheme. This amplitude, valid up-to next-to-next-leading order in the chiral expansion, systematically includes the effects of the $Δ(1232)$, giving a reliable description of the phase shifts of different partial wave analyses up to energies just below the resonance region. We obtain predictions on some observables that are within experimental bounds and phenomenological expectations. In particular, we use the center-of-mass energy dependence of the amplitude adjusted with the data above threshold to extract accurately the value of $σ_{πN}$. Our study indicates that the inclusion of modern meson-factory and pionic-atom data favors relatively large values of the sigma term. We report the value $σ_{πN}=59(7)$ MeV.

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英文摘要：

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