arXiv 2409.051292024-09nucl-thhep-ph

核透明度和两步过程在$A(e,e'π^+)$反应中的阴影效应

Nuclear transparency and shadowing of the two-step process in the $A(e,e'π^+)$ reaction

Yonsei University（延世大学）；Korea Aerospace University（韩国航空大学）

Tae Keun Choi, Kook-Jin Kong, Byung-Geel Yu

备注：: 7 pages, 4 figures, 1 table
发表信息：: Phys. Rev. C 111, 064608 (2025)

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AI总结：

研究了$A(e,e'π^+)$反应中核透明度与两步过程的阴影效应，通过量子扩散模型和阴影效应解释了透明度随$Q^2$变化的机制。

摘要：

我们研究了介子电产生于核中的核透明度，$A(e,e'π^+)$，重点在于两步过程在Glauber多重散射理论中的作用。基于将量子扩散模型纳入Glauber理论的框架，分析了光子虚能范围$0.5< Q^2< 10$ GeV$^2/c^2$的实验数据，包括最近在6 GeV电子束下的JLab数据以及12 GeV升级的提案。在夸克/反夸克$(q\bar{q})$结构形成长度内应用量子扩散模型，再现了核透明度在高$Q^2$下的增加，显示了颜色透明度的证据。相比之下，通过γ*波动到ρ^0的相干长度，两步过程通过选择ρN散射截面为σ_{ρN}=σ_{πN}，在Q^2整个范围内导致核透明度的降低。结合通常在Glauber理论原始公式中采用的一步过程（直接光子耦合），该反应机制通过初始态相互作用中的阴影效应，提供了低虚能下透明度$Q^2$依赖性的另一个来源。通过进一步的吸收由于阴影，对于$^{12}$C、$^{27}$Al、$^{63}$Cu和$^{197}$Au核的介子透明度测量得到了更好的一致。讨论了透明度$T_A=A^{α-1}$参数$α$的$Q^2$依赖性。

英文摘要：

We investigate nuclear transparency induced by pion electroproduction on nuclei, $A(e,e'π^+)$, with our interest in the role of the two-step process in the Glauber multiple scattering theory. Based on the framework in which the quantum diffusion model is incorporated into the Glauber theory, the experimental data in the range of photon virtuality $0.5< Q^2< 10$ GeV$^2/c^2$ are analyzed, including the recent JLab data at the 6 GeV electron beam together with the proposal for the 12 GeV upgrade. Application of the quantum diffusion model during the formation length of the quark/antiquark $(q\bar{q})$ structure of a pion reproduces the increase in the nuclear transparency up to high $Q^2$, showing evidence of color transparency. In contrast, through the coherent length of the $γ^*$ fluctuation into $ρ^0$, the two-step process with the $ρN$ scattering cross section chosen to be $σ_{ρN}=σ_{πN}$ contributes to a reduction of the nuclear transparency in the whole range of $Q^2$. Combined with the one-step process (direct photon coupling) usually adopted in the original formulation of the Glauber theory, this reaction mechanism provides another source of the $Q^2$ dependence of the transparency at low virtualities through the shadowing in the initial state interaction. By the further absorption due to the shadowing, a better agreement is obtained with the pion transparency measured in the $A(e,e'π^+)$ reaction for $^{12}$C, $^{27}$Al, $^{63}$Cu, and $^{197}$Au nuclei. A discussion of the $Q^2$ dependence of the parameter $α$ for the transparency $T_A=A^{α-1}$ is given.

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