大Nf下的手征对称性破缺及共形窗口附近rho介子的性质
Chiral symmetry breaking for large "Nf" and the properties of the "rho" meson near the conformal window
浏览论文内容
中文总结 AI 辅助
研究轻夸克味道数N_f趋近共形窗口时rho介子基态性质的变化，发现其质量随组分标度收缩、衰变常数软化、形状因子变平且半径增大，解离由禁闭长度发散控制。
中文摘要 AI 辅助
我们研究了当轻夸克味道数N_f被推向共形窗口时，rho介子基态性质如何响应。相互作用是一种保持对称性、禁闭的矢量-矢量接触相互作用，其有效耦合具有味道依赖性，旨在编码费米子圈在深红外区域产生的屏蔽效应。该相互作用输入到戴森-施温格方程（用于描述穿衣服的夸克传播子）以及彩虹-阶梯截断下的齐次贝特-萨尔皮特方程中，并在施温格固有时方案中正则化，从而在保持手征对称性破缺的同时消除夸克产生阈值。增加N_f会减弱耦合，抑制动态生成的质量，并在临界味道数N^{c}_{f}处恢复手征对称性以及退禁闭。矢量道与赝标量道的响应不同。由于rho介子不是戈德斯通玻色子，其质量不受正在恢复的对称性保护，它只是跟随收缩的组分标度，而正则归一化的振幅E_rho和轻子衰变常数f_rho在此过程中变软。在此框架下，对于所考察的每个味道数，rho介子都位于名义上的q\ar{q}阈值之上，因此该态只有在禁闭移除该阈值时才能存活。因此，解离由禁闭长度标度的发散控制，而非束缚态质量的穿越，我们对这两种判据进行了对比。在广义冲量近似下计算的三个弹性电磁形状因子G_E、G_M和G_Q随着N_f增大而变平，G_E的过零点向红外方向迁移，电荷半径增大，而四极矩的幅度减小。因此，随着理论接近共形性，rho介子变得更大更圆。
英文摘要
We study how the ground-state properties of the rho meson respond when the number of light-quark flavors N_f is driven towards the conformal window. The interaction is a symmetry-preserving, confining vector--vector contact interaction whose effective coupling carries a flavor dependence designed to encode the screening produced by fermion loops in the deep infrared. That interaction feeds the Schwinger--Dyson equation for the dressed-quark propagator and the homogeneous Bethe--Salpeter equation in the rainbow-ladder truncation, regularized in the Schwinger proper-time scheme so that quark production thresholds are absent while chiral symmetry remains broken. Raising N_f weakens the coupling, suppresses the dynamically generated mass and restores chiral symmetry together with deconfinement at a critical flavor number N^{c}_{f}. The vector channel responds differently from the pseudoscalar one. Because the $ρ$ is not a Goldstone boson, its mass is not protected by the symmetry that is being restored, and it simply follows the shrinking constituent scale, while the canonically normalized amplitude E_rho and the leptonic decay constant f_rho soften along the way. In this framework the rho sits above the nominal q\bar{q} threshold for every flavor number examined, so the state survives only as long as confinement removes that threshold. Dissociation is therefore governed by the divergence of the confinement length scale rather than by a crossing of the bound-state mass, and we contrast both criteria. The three elastic electromagnetic form factors G_E, G_M and G_Q, computed in the generalized impulse approximation, flatten as N_f grows, the zero crossing of G_E migrates towards the infrared and the charge radius expands, whereas the magnitude of the quadrupole moment decreases. The rho thus becomes a larger and rounder object as the theory approaches conformality.
发表机构
- Institute of Physics, Gomal University（哥马尔大学物理研究所）
- Facultad de Ciencias Físico-Matemáticas, Benemérita Universidad Autónoma ed Chiapas（恰帕斯自治优秀大学物理数学科学学院）
- Facultad de Ingeniería Eléctrica, Universidad Michoacana de San Nicolás de Hidalgo（米乔阿肯圣尼古拉斯德伊达尔戈大学电气工程学院）
- Centro de Ciencias Exactas, Universidad del Bío-Bío（比奥比奥大学精确科学中心）
- Department of Physics, University of Science and Technology, Bannu（班努科技大学物理系）
机构由 AI 辅助整理，请以论文原文为准。
