发表机构
Department of Physics Education, Teachers College, Kyungpook National University（庆北国立大学教师教育学院物理教育系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过比较BT构造与协变BS模型，证明在光前动力学中BT实现可实现赝标量跃迁形状因子的电流分量独立性，并解析建立等价性，阐明零模的动力学来源。
AI 中文摘要
我们考察了Bakamjian--Thomas（BT）构造在光前（LF）动力学中实现赝标量到赝标量半轻子形状因子的电流分量独立性中的作用。一个精确可解的协变Bethe--Salpeter（BS）模型提供了一个离壳基准。其横向电流零模贡献直接从收缩的非价区计算，并由价卷积中的有效算符再现。在基于BT的光前夸克模型中，单体电流核由壳上组分旋量构造，而相互作用编码在质量算符和波函数中。在该实现中，$(+,\perp)$电流分量提取无零模，并由壳上重叠饱和。在内部投影中一致地使用自由组分不变质量，在积分后从$(+,\perp)$和$(+,-)$电流分量提取得到相同的$f_-(q^2)$。对于旋转不变的径向波函数，在LF雅可比行列式和所采用的赝标量自旋耦合下，只要约化重叠收敛，我们解析地建立了这一等式。与使用物理介子质量的负电流投影的差异定义了一个依赖于相互作用的BT补全，不同于BS端点贡献。一个质量加权的复横向轮廓允许在整个物理类时间区间（包括零反冲）直接评估高斯$D\to K$重叠，无需形状因子参数化或外推。这些结果在指定的BT实现中确立了电流分量独立性，并阐明了零模分配的动力学依赖性。
英文摘要
We examine the role of the Bakamjian--Thomas (BT) construction in achieving current-component independence for pseudoscalar-to-pseudoscalar semileptonic form factors in light-front (LF) dynamics. An exactly solvable covariant Bethe--Salpeter (BS) model provides an off-shell benchmark. Its transverse-current zero-mode contribution is calculated directly from the shrinking nonvalence region and reproduced by an effective operator in the valence convolution. In the BT-based LF quark model, the one-body current kernel is constructed from on-shell constituent spinors, while interactions are encoded in the mass operator and wave functions. In this realization, the $(+,\perp)$ current-component extraction is zero-mode free and is saturated by the on-shell overlap. Using the free constituent invariant masses consistently in the internal projections yields the same $f_-(q^2)$ from the $(+,\perp)$ and $(+,-)$ current-component extractions after integration. We establish this equality analytically for rotationally invariant radial wave functions with the LF Jacobian and the adopted pseudoscalar spin coupling, provided the reduced overlaps converge. The difference from the minus-current projection using physical meson masses defines an interaction-dependent BT completion, distinct from the BS endpoint contribution. A mass-weighted complex transverse contour permits direct evaluation of the Gaussian $D\to K$ overlaps throughout the physical timelike interval, including zero recoil, without a form-factor parametrization or extrapolation. These results establish current-component independence within the specified BT realization and clarify the dynamical dependence of zero-mode assignments.
Comments27 pages, 2 figures
