| Project/Area Number |
12640248
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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 |
素粒子・核・宇宙線
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| Research Institution | Tohoku University |
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Principal Investigator |
HIKASA Ken-ichi Tohoku University, Dept. of Physics, Professor, 大学院・理学研究科, 教授 (20208739)
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| Co-Investigator(Kenkyū-buntansha) |
SUMINO Yukinari Tohoku University, Dept. of Physics Assistant, 大学院・理学研究科, 助手 (80260412)
YAMADA Youichi Tohoku University, Dept. of Physics Assistant, 大学院・理学研究科, 助手 (00281965)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | elementary particle / top quark / collider / super symmetry / high energy physics / ヒッグス粒子 / QCD / くりこみ / 中性カレント |
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| Research Abstract |
1. Precise determination of the top quark mass may be made by measuring the cross section of the process e^+e^- → tt^^- near threshold. We find that theoretical error in the determination can be made small by using the <MS>^^^- mass instead of the pole mass as the parameter representing the top quark mass.
2. We examine the bottomonium spectrum using higher order perturbative QCD calculation and find that the theory reproduces the data quite well, in contrary to the belief that perturbation theory is not applicable.
3. We study the decay of the top squark in the mass region where the direct decay to the top quark is not kinematically allowed. We calculated the decay to a charm squark a neutralino via flavor-changing neutral current in the supergravity model by solving renormalization group equations. We show that this mode can be dominant when the parameter tan β is large. We further examine the case this mode competes with the charged current decay to a bottom squark and a chargino and propose a method to detect the top squark pair production events at hadron colliders
4. Definition of the mixing matrix is nontrivial at higher orders in perturbation theory. We examine the gauge dependence of the mixing matrix and explicitly calculated the correction in several examples.
5. It is known that the QCD correction for the decay of a Higgs boson to quarks and squarks is rather large. We find that a clever choice of the lowest-order parameter can reduce the size of the correction, leading to more reliable theoretical predictions.
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