2001 Fiscal Year Final Research Report Summary
Precise computation of weak matrix elements of B meson with lattice QCD
| Project/Area Number |
12640279
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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 | Kyoto University (2001)
Hiroshima University (2000) |
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Principal Investigator |
ONOGI Tetsuya Yukawa Institute for theoretical Physics, Kyoto University, Associate Professor, 基礎物理学研究所, 助教授 (70211802)
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| Co-Investigator(Kenkyū-buntansha) |
HASHIMOTO Shoji Computational Science Center, High Energy Accelaterator Research Organization, Assistant, 計算科学センター, 助手 (90280510)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Lattice QCD / B meson / Kobayashi-Masukawa matrix |
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| Research Abstract |
1. We computed the decay constant for the B meson using nonrelativistic effective theory (NRQCD) in quenched approximation and obtained the following results
f_<B_d> = 170 ± 5 ± 15 Mev, f_<B_s>/f_<B_d> = 1.12 ± 2 ± 1^<+3>_<-0>
We also computed the one-loop renormalization factors for the ΔB = 2 four-fermi operators which are necessary for the bag parameter calculation. Using the same technique as for the decay constant, we obtained the quenched results for the bag paramter B_B, B_S as follows
B_B(m_b) = 0.85 ± 0.03 ± 0.11, B_<B_s>/B_<B_d> = 1.01 ± 0.01 ± 0.03, B_S(m_b)/R^2(m_b) = 1.24 ± 0.03 ± 0.16.
Using our results and the experimental data from Belle, Babar and BTeV, we expect to extract CKM matrix elements |V_<td>, |V_<ts>|.
2. We studied the form factors for the semileptonic decay B → πlv with NRQCD in quenched approximation and obtained the following results
∫^<q^2_<max>>_<q^2=18GeV^2> (dΓ)/(dq^2) =|V_<ub>|^2[1.18 ± 0.37 ± 0.08 ± 0.31]psec^<-1>.
Using our results and the experimental da
… More
ta from Bell and Babar which will appear near future, we expect to extract CKM matrix elements |V_<ub>|.
3. We studied the hadron matrix element of nucleon to light mesons with the baryon number violating operators which is crucial to the nucleon decay in the grand unified theories in quenched lattice QCD. We found that our results give 4 〜 5 times larger amplitudes than the most conservative values in quark model estimate. Our theoretical results for the nucleon decay gives much stronger limit on the SUSY GUT models and completely killed the minimal SUSY SU(5) GUT.
4. We proposed a new formulation of heavy quark on the anisotropic lattice in order to look for the possibility of calculating heavy-light weak matrix elements with much higher precision than the present effective theory approach. We found that using the anisotropic lattice the mass dependence of the renormalization factors is drastically reduced. We also obtained preliminary results which suggests that one can compute the mass spectrum and simple matrix elements with few percent accuracy after controlling systematic errors for the calibration of anisotropy parameters. Less
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Research Products
(23 results)
