2005 Fiscal Year Final Research Report Summary
Study of novel spin structure of the proton and the neutron at HERMES
| Project/Area Number |
16340070
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Tokyo Institute of Technology |
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Principal Investigator |
SHIBATA Toshi-aki Tokyo Institute of Technology, Graduate School of Science, Professor (80251601)
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| Co-Investigator(Kenkyū-buntansha) |
MIYACHI Yoshiyuki Tokyo Institute of Technology, Gradutate School of Science, Assistant Professor (50334511)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Spin / Quark / Proton / Neutron / Deep Inelastic Scattering / Gluon / Elementary Particle / Electron |
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| Research Abstract |
The proton is basically composed of three quarks. But it is known that the quark spin contribution to the proton spin is small. It is called 'proton spin problem'. This is based on the discovery made by EMC at CERN about 20 years ago. HERMES experiment is an international collaboration from 11 countries to study this problem with unique technical capabilities. Electron or positron beam of DESY-HERA of 27.6 GeV and internal gas targets are used. Deep-inelastic scattering of electron off the nucleon is measured. The HERMES detects the scattered electron and also produced hadrons. For the hadron identification, the RICH(ring imaging Cherenkov detector) plays the main role.
In 2004-2005, we published the results of flavor decomposition of the helicity distribution function. The polarization of u quark is positive while the polarization of d quark is negative. The polarization of s quark and anti-quarks are consistent with zero.
Next, we published a result from the transversely polarized target. We succeeded to identify Sivers effect and Collins effect by measuring angular correlation between the scattered electron and produced hadrons. The result suggests non-zero orbital angular momentum. This result was presented in international conferences as well as in the paper and attracted a large attention.
The deuteron is a spin 1 particle, thus it can have the tensor structure function. It is called b1(x). We actually measured it for the first time. This opened a new field of research for experiments and theories.
We published the detailed description of the polarized gas internal targets which is the key element of the HERMES experiment.
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Research Products
(75 results)
