2006 Fiscal Year Final Research Report Summary
MEDIUM MODIFICATIONS OF NUCLEON STRUCTURE FUNCTIONS
| Project/Area Number |
16540267
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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 |
WOLFGANG BENTZ TOKAI UNIVERSITY, SCHOOL OF SCIENCE, PROFESSOR, 理学部, 教授 (20168769)
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| Co-Investigator(Kenkyū-buntansha) |
YAZAKI KOICHI TOKYO WOMAN'S CHRISTIAN UNIVERSITY, COLLEGE OF ARTS AND SCIENCES, PROFESSOR, 文理学部, 教授 (60012382)
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| Project Period (FY) |
2004 – 2006
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| Keywords | quarks / hadrons / structure functions / medium modifications / deep inelastic scattering / polarized scattering / equation of state / nuclear structure |
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| Research Abstract |
Between April 2005 and March 2007, the following research results have been obtained :
1) Viewing the nucleon as a relativistic 3-quark system, we described it as a bound state of a scalar or axial vector diquark and a quark (papers No. 1,2). We determined the quark distribution functions in the nucleon, as well as the unpolarized and polarized nucleon structure functions. We compared our results to experimental data on deep inelastic scattering, and to empirical distribution functions. We pointed out that our quark-diquark model can describe the structure functions of a single nucleon very well.
2) We assessed the medium modifications of the nucleon structure functions, and calculated the structure functions of finite nuclei (papers No.3,4). By combining our nuclear matter equation of state, which takes into account the quark substructure of the nucleons, with the model of the nucleon described above, we calculated the quark distribution functions in the nuclear medium. We compared the
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unpolarized quark distributions to the polarized ones, and pointed out that the medium modification of the polarized ones (the polarized EMC effect) is larger. In order to determine the nuclear structure functions, we made use of the mean field approximation for the nuclear systems, and of the quark-diquark model for the nucleon. We found that the vector mean field in the nucleus plays a very important role in the description of the unpolarized nuclear structure functions. After reproducing the experimental data on unpolarized lepton-nucleus deep inelastic scattering quantitatively, we made predictions for the polarized nuclear structure functions within our model. We also discussed several nuclei for which experimental measurements would be feasible, thereby giving a strong impact on future experiments with polarized lepton beams.
3) We described also other high energy scattering processes, thereby extending the range of applicability of our model (papers No. 5,6). We assessed the medium modifications of the nucleon form factors, and calculated the response functions for quasielastic electron-nucleus scattering. We also calculated the generalized parton distributions, which play an important role for particle productions in deep inelastic scattering processes (exclusive processes). We showed that the diquark correlations in the nucleon play a very important role in the description of these high energy processes. Less
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