论文标题
分散改善的手性有效场理论，核子中的横向电荷和电流密度
Transverse charge and current densities in the nucleon from dispersively improved chiral effective field theory
论文作者
论文摘要
背景：横向密度$ρ_{1，2}（b）$描述电荷和磁矩在固定轻段时间的分布，并将核子的弹性形式变量与其派对结构联系起来。形式因素的分散表示$ f_ {1，2}（t）$在$ t $ channel中的辐射状态的交换方面表达了密度，并允许使用HADRONIC PHACTIONAICS方法进行分析。 目的：计算外围距离处的密度$ b = \ MATHCAL {O}（M_π^{ - 1}）$，其中它们主要由分散表示中的两个二值状态生成。量化不确定性。 方法：分散改进的手性有效场理论（DI $χ$ eft）用于计算两杆剪切上的等级频谱函数$ \ textrm {im} \，f_ {1，2}（t）$。该方法包括$ππ$互动（$ρ$共振）通过弹性liTarity，并提供最高$ t \ $ 1 GEV $^2 $的逼真的光谱功能。高质量状态通过有效的极点参数化，并受到总和规则（电荷，半径，超级范围关系）的约束。密度$ρ_{1，2}（b）$是从其分散表示。通过改变光谱函数来量化不确定性。该方法尊重分析性，并确保密度的正确$ b \ rightarrow \ infty $渐近行为。 结果：在所有距离上获得准确的密度$ b \ gtrsim 0.5 $ fm，正确的行为降至$ b \ rightarrow 0 $。在横核结构受两杆状态控制的情况下，定量距离区域。计算和讨论了极化核中的光线电流分布。 结论：可以使用di $χ$ EFT从第一原理计算外围核子结构。该方法可以扩展到广义的Parton分布和其他核子形式。
Background: The transverse densities $ρ_{1, 2}(b)$ describe the distributions of electric charge and magnetic moment at fixed light-front time and connect the nucleon's elastic form factors with its partonic structure. The dispersive representation of the form factors $F_{1, 2}(t)$ expresses the densities in terms of exchanges of hadronic states in the $t$-channel and permits their analysis using hadronic physics methods. Purpose: Compute the densities at peripheral distances $b = \mathcal{O}(M_π^{-1})$, where they are generated predominantly by the two-pion states in the dispersive representation. Quantify the uncertainties. Methods: Dispersively improved chiral effective field theory (DI$χ$EFT) is used to calculate the isovector spectral functions $\textrm{Im}\, F_{1, 2}(t)$ on the two-pion cut. The method includes $ππ$ interactions ($ρ$ resonance) through elastic unitarity and provides realistic spectral functions up to $t \approx$ 1 GeV$^2$. Higher-mass states are parametrized by effective poles and constrained by sum rules (charges, radii, superconvergence relations). The densities $ρ_{1, 2}(b)$ are obtained from their dispersive representation. Uncertainties are quantified by varying the spectral functions. The method respects analyticity and ensures the correct $b \rightarrow \infty$ asymptotic behavior of the densities. Results: Accurate densities are obtained at all distances $b \gtrsim 0.5$ fm, with correct behavior down to $b \rightarrow 0$. The region of distances is quantified where transverse nucleon structure is governed by the two-pion state. The light-front current distributions in the polarized nucleon are computed and discussed. Conclusions: Peripheral nucleon structure can be computed from first principles using DI$χ$EFT. The method can be extended to generalized parton distributions and other nucleon form factors.
