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arXiv 0712.2079hep-phhep-exnucl-ex
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核子自旋含量及其尺度依赖性的唯象分析

Phenomenological analysis of the nucleon spin contents and their scale dependence

M. Wakamatsu, Y. Nakakoji

摘要:

在过去的几年中,大量的证据表明核子内部的胶子极化至少在低重整化标度下是很小的。另一方面,最近的格点量子色动力学分析表明夸克携带的净轨道角动量几乎为零。布罗德斯基和加德纳也注意到,根据COMPASS观测到的等熵氘靶上的小单自旋不对称性,核子内部的胶子轨道角动量可能很小。简单地把所有这些观察结果结合起来,我们会得出一个相当尴尬的结论,即核子组分总共没有携带足够的角动量来饱和核子的总自旋。我们表明,这种有点混乱的事态可以澄清,只有仔细注意核子自旋分解的尺度依赖性。

英文摘要:

In the past few years, a lot of evidences have been accumulated, which indicate that the gluon polarization inside the nucleon is likely to be small at least at the low renormalization scales. On the other hand, the recent lattice QCD analyses suggest that the net orbital angular momentum carried by the quarks is nearly zero. There is also some indication noticed by Brodsky and Gardner based on the COMPASS observation of small single-spin asymmetry on the isoscalar deuteron target, that the gluon orbital angular momentum inside the nucleon is likely to be small. Naively combining all these observations, we are led to a rather embarrassing conclusion that the nucleon constituents altogether do not carry enough amount of angular momentum saturating the total nucleon spin. We show that this somewhat confused state of affairs can be cleared up only by paying careful attention to the scale dependencies of the nucleon spin decomposition.

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