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Nuclear parton distributions and structure functions

核部分子分布和结构函数

基本信息

批准号：
19540306
负责人：
BENTZ Wolfgang
金额：
$ 1.75万
依托单位：
Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2007
资助国家：
日本
起止时间：
2007 至 2009
项目状态：
已结题

项目摘要

The parton distributions and structure function of a nucleon bound in the nucleus are different from the case of a free nucleon. We assessed these medium effects quantitatively, and performed calculations for several nuclear targets. We also evaluated the fragmentation functions, which describe meson production in deep inelastic scattering processes.For our model calculations, we used the Nambu-Jona-Lasinio (NJL) model to describe the nucleon as a 3-quark bound state. Nuclear matter and finite nuclei were described in the mean field approximation, taking into account the internal quark structure of the nucleons. The parton distributions in the nuclear medium were obtained by a convolution of the parton distributions in the single nucleon and the nucleon distributions in the medium. Using this method, we predicted the spin-dependent parton distributions for several nuclei, and pointed out the importance of medium modifications. We also assessed the flavor dependence of the nuclear parton distributions, and applied our results to deep inelastic neutrino scattering from nuclear targets (NuTeV experiment) and parity-violating electron scattering. One of our main conclusions was that the famous problem of the NuTeV anomaly can be solved by taking into account the medium modifications of parton distributions.For the description of the fragmentation functions we also used the NJL model. We described pion production in semi-inclusive high energy scattering processes, taking into account the multifragmentation processes in the framework of the jet-model. We compared our results with recent analyses of semi-inclusive pion production data, and pointed out the important role of the multifragmentation processes.

束缚在原子核中的核子的分子分布和结构函数与自由核子的情况不同。我们定量地评估了这些介质效应，并对几个核目标进行了计算。我们还评估了描述深度非弹性散射过程中介子产生的碎片函数。对于我们的模型计算，我们使用Nambu-Jona-Lasinio （NJL）模型将核子描述为3夸克束缚态。考虑到核子的内部夸克结构，用平均场近似描述了核物质和有限核。核介质中的部分子分布由单核子中的部分子分布与介质中的核子分布进行卷积得到。利用这种方法，我们预测了几种原子核的自旋相关的部分子分布，并指出了介质修饰的重要性。我们还评估了核部分子分布的风味依赖性，并将我们的结果应用于核目标的深度非弹性中微子散射（NuTeV实验）和违反宇称的电子散射。我们的主要结论之一是，可以通过考虑部分子分布的介质修正来解决著名的NuTeV异常问题。对于碎片函数的描述，我们也使用了NJL模型。我们描述了半包容高能散射过程中介子的产生，并考虑了射流模型框架中的多重破碎过程。我们将我们的结果与最近对半包容介子生产数据的分析进行了比较，并指出了多重破碎过程的重要作用。