| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
The U(1) problem is one of outstanding issues in elementary particle physics. We try to reproduce masses of pseudo-scalars eta and eta-prime, which is much heavier than the pi, using lattice full QCD simulations in which all light quarks u, d, s are treated dynamically.
We expect that the large mass of the eta and eta-prime originates from topological non-trivial structure of QCD, which is realized through pair creation/annihilation of light quarks. In addition, physical states are mixing states of octet and singlet pseudo scalars. In order to derive masses correctly from QCD, we have to treat all quarks dynamically.
In this research, we use full QCD configurations generated by the CP-PACS and JLQCD collaborations, which have already been used for a study of flavor non-singlet hadron spectrum. Calculations are carried out as follows. 1) We evaluate disconnected diagram using stochastic noise estimator technique (SET). 2) In order to extract eta and eta-prime signals from propagators, we combine smearing method with the SET. 3) Propagator matrix among the flavor SU(2) singlet and strange pseudo-scalars are diagonalized to dissolve mixing and determine physical masses of the eta and eta-prime.
Eta mass extrapolated to the physical point turns out to be 0.545(16) GeV, which agrees well with experiment. Eta-prime mass 0.871(46) GeV is much larger than the pion mass, and only 0.1 GeV below the experimental value. They are very encouraging, although these results are obtained only on one lattice spacing. We plan to carry out similar calculations for finer lattices and determine masses of the eta and eta-prime in the continuum limit.
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