标题： 核子-核子有效场论在NNLO：辐射介子和1S0相移 显示英文标题

标题： Nucleon-Nucleon Effective Field Theory at NNLO: Radiation Pions and 1S0 Phase Shift

摘要： 低能涉及两个核子的现象可以使用有效场论成功描述。 由于相对较大的展开参数，只有在次次领头阶（NNLO）才能期望与实验在百分之几的水平上达成一致。 本次演讲的第一部分将关注辐射介子效应，这些效应首次出现在NNLO。 对于质心动量p~\sqrt{M m_pi}=Q_r（介子产生的阈值），辐射介子的功率计数是简单的。 我们解释了如何用Q_r功率计数计算的图在p~m_\pi 时的尺度。 Q_r^3的辐射介子对核子-核子散射的贡献被S波散射长度的逆幂所抑制。 然而，我们指出Q_r^4的辐射贡献可能在p~m_pi时给出NNLO贡献。 在演讲的第二部分，介绍了NNLO 1S0相移中势介子和接触相互作用部分的结果。 我们强调在微扰展开的每一阶消除虚假极点的重要性。 这样做后，在NNLO只剩下三个自由参数。 我们得到了对1S0相移的良好拟合。 显示英文摘要

摘要： 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.