Spectral functions of nucleon form factors: Three-pion continua at low energies
Spectral functions of nucleon form factors: Three-pion continua at low energies
复制标题
DOI：
10.1140/epja/i2019-12680-y
复制
发表时间：
2019-01
期刊：
影响因子：
--
通讯作者：
N. Kaiser;E. Passemar;E. Passemar
中科院分区：
文献类型：
--
作者：
N. Kaiser;E. Passemar;E. Passemar
研究了协变重子手性微扰理论中接近阈值的核子等标量电磁和等矢量轴形因子的虚部。在双环水平上，计算了由领先和次领先阶手性顶点以及虚拟等压线的介子激发引起的贡献。发现重子处理实质上高估了这些连续体。从现象学分析，包括窄共振或宽共振，可以识别出阈值附近的小窗口，其中手性动力学占上风。然而，在等标量电磁形状因子的情况下，中间态提供的辐射校正结果是相似的大小。
We study the imaginary parts of the isoscalar electromagnetic and isovector axial form factors of the nucleon close to the-threshold in covariant baryon chiral perturbation theory. At the two-loop level, the contributions arising from leading and next-to-leading order chiral-vertices, as well as pion-induced excitations of virtual-isobars, are calculated. It is found that the heavy baryon treatment overestimates substantially these-continua. From a phenomenological analysis, that includes the narrow-resonance or the broad-resonance, one can recognize small windows near threshold, where chiral-dynamics prevails. However, in the case of the isoscalar electromagnetic form factors, the radiative correction provided by the-intermediate state turns out to be of similar size.