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arXiv 1104.1830nucl-exhep-exhep-phnucl-th
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强子性质的介质修正与部分子过程

Medium Modifications of Hadron Properties and Partonic Processes

W. K. Brooks, S. Strauch, K. Tsushima

备注：
to appear in J. Phys.: Conf. Proc. "New Insights into the Structure of Matter: The First Decade of Science at Jefferson Lab", eds. D. Higinbotham, W. Melnitchouk, A. Thomas; added references
发表信息：
J.Phys.Conf.Ser.299:012011,2011
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摘要：

手征对称性是QCD中最基本的对称性之一。它通过夸克凝聚体<bar{q}q>的约化与核介质中的强子性质密切相关，表现为手征对称性的部分恢复。为了更好地理解这一重要问题，杰斐逊实验室在过去十年中的许多实验都集中在理解核介质中介子和核子的性质上，通常受益于CEBAF加速器的高偏振和亮度。特别是，一种新的，准确的，极化转移测量技术首次揭示了一个强烈的迹象表明，绑定质子电磁形状因子在4 He可以修改相比，在真空中。第二，通过测量矢量介子在不同核上的光生，研究介质中对ρ介子性质的影响。在这个实验中，没有观察到明显的质量位移和一些与预期的ρ介子碰撞增宽一致的增宽，这对模型计算提供了严格的限制。最后，涉及在介质中的部分子传播的过程进行了研究。介质修改的夸克碎裂函数已被提取具有更高的统计精度比以前可能的。

英文摘要：

Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate <bar{q}q>, manifesting the partial restoration of chiral symmetry. To better understand this important issue, a number of Jefferson Lab experiments over the past decade have focused on understanding properties of mesons and nucleons in the nuclear medium, often benefiting from the high polarization and luminosity of the CEBAF accelerator. In particular, a novel, accurate, polarization transfer measurement technique revealed for the first time a strong indication that the bound proton electromagnetic form factors in 4He may be modified compared to those in the vacuum. Second, the photoproduction of vector mesons on various nuclei has been measured via their decay to e+e- to study possible in-medium effects on the properties of the rho meson. In this experiment, no significant mass shift and some broadening consistent with expected collisional broadening for the rho meson has been observed, providing tight constraints on model calculations. Finally, processes involving in-medium parton propagation have been studied. The medium modifications of the quark fragmentation functions have been extracted with much higher statistical accuracy than previously possible.

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