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arXiv 0709.4034nucl-ex
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~ 4 He(e,e 'p)~ 3 H反应中质子介质修正的研究

Search for Proton Medium Modifications in the 4He(e,e'p)3H Reaction

S. Strauch

摘要:

准弹性核子敲除中的极化转移对核子在核介质中的性质敏感,包括核子形状因子和/或旋量的可能修改。在杰斐逊实验室最近完成的实验E03-104中,我们以前所未有的精度测量了Q^2为0.8(GeV/c)^2和1.3(GeV/c)^2时4 He(e,e 'p)3 H反应中质子的反冲极化。这些数据补充了美因茨实验室和杰斐逊实验室在0.4 ~ 2.6(GeV/c)^2之间的早期数据。测量的极化转移系数的比率不同于完全相对论计算,有利于包括介质修改的质子形状因子预测的夸克-介子耦合模型或强电荷交换的最终状态相互作用。测得的诱导极化与完全相对论计算吻合得很好,表明这些强的末态相互作用可能不适用。

英文摘要:

Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the 4He(e,e'p)3H reaction at a Q^2 of 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2 with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c)^2 from both Mainz and Jefferson Lab. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring either the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model or strong charge-exchange final-state interactions. The measured induced polarizations agree well with the fully relativistic calculation and indicate that these strong final-state interactions may not be applicable.

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