2009 Fiscal Year Final Research Report
Nuclear parton distributions and structure functions
| Project/Area Number |
19540306
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Tokai University |
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Principal Investigator |
BENTZ Wolfgang Tokai University, 理学部, 教授 (20168769)
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| Co-Investigator(Renkei-kenkyūsha) |
YAZAKI Koichi 独立行政法人理化学研究所, 延興放射線研究室, 客員主管研究員 (60012382)
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| Project Period (FY) |
2007 – 2009
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| Keywords | ハドロン物理学 / クォーク / クォーク有効理論 / 構造関数 / 媒質効果 / 破砕関数 |
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| Research Abstract |
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.
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