NUMERICAL STUDY OF LATTICE QUANTUM CHROMODYNAMICS

晶格量子色动力学的数值研究

• 批准号: 06640372
• 负责人: UKAWA Akira
• 金额: $ 1.15万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640372/
• 关键词: PARTCLE PHYSICS; STRONG INTERACTIONS; LATTICE QCD; NUMERICAL SIMULATION; WEAK INTERACTION; CP VIOLATION; CKM MATRIX; B MESON; 量子色力学; 格子ゲージ理論

Numerical simulations of lattice QCD provides a viable method for determination of the strong interaction corrections to weak amplitudes of hadrons, which is crucial for elucidating unsolved problems of weak interactions of elementary particles including the origin of CP violation. The objective of the present research is to carry out a systematic study of lattice QCD in this direction.In 1994 we applied the method of wall source without gauge fixing, previously developed by us, to the problem of pi-N sigma term and the quark content of proton spin. Both these matrix elements receive contributions from sea quark loops, and how one can evaluate these contributions represents a general problem that also appear in weak matrix element calculations. We found that the method works well, and that the values obtained are consistent with experiments, strongly indicating for the first time that QCD successfully explains the values of these observables long debated in particle theory.In the same … More year we also started preparations for Fujitsu VPP500/80 vector parallel supercomputer, which was scheduled to be installed at KEK in January 1995. A variety of lattice QCD codes were written, and tested intensively in the period January-March 1995.In April 1995 we have initiated large scale lattice QCD calculations of a variety of weak matrix elements of hadrons on VPP.The present status of the calculations are as follows.(1) The K Meson B parameter is one of the fundamental quantity for fixing the Cabibbo-Kobayashi-Maskawa quark mixing matrix. A quenched calculation of this quantity with the Kogut-Susskind quark action is well underway. So far data for 6 values of lattice spacings have been collected, and a calculation for one more value of lattice spacing is planned. Together the data should allow a precision extrapolation of the B parameter to the continuum limit. A similar calculation with the Wilson quark action, based on the method of chiral Ward identities developed this year, is also underway.(2) Another parameter important for CP violation studies is the B meson decay constant. An initial calculation made in the early summer of 1995 revealed large statistical fluctuations. A method of smeared source for reducing the error was tested, and a new calculation has been started late 1995. Data for two values of lattice spacing have been collected and a further calculations with reduced lattics spacing is planned to start soon. This will allow us to estimate the continue m value of the decay constant.(3) Tests of Clover quark action, expected to have a faster approach to the continuum limit, has been completed. Real calculations will start as soon as the Wilson calculation in (2) will be finished.We expect to be able to publish final results of these calculations by summer of 1996. Less

晶格QCD的数值模拟为确定强子弱振幅的强相互作用修正提供了一种可行的方法，这对于阐明基本粒子的弱相互作用包括CP破坏的起源等悬而未决的问题至关重要。本研究的目的就是在这个方向上对晶格QCD进行系统的研究。1994年，我们将我们以前发展的无规范的壁源方法应用于pi-N sigma项和质子自旋的夸克含量问题。这两个矩阵元素都接受来自海夸克循环的贡献，如何评估这些贡献是一个普遍存在的问题，也出现在弱矩阵元素计算中。我们发现这种方法很好地工作，并且得到的值与实验相一致，这有力地表明QCD第一次成功地解释了这些在粒子理论中长期争论的观察量的值。在相同的…中多年来，我们还开始准备富士通VPP500/80矢量并行超级计算机，计划于1995年1月在KEK安装。1995年1-3月，我们编写了各种格子QCD码，并进行了密集的测试。1995年4月，我们对强子的各种弱矩阵元进行了大规模的格子QCD计算。计算现状如下：(1)K介子B参数是确定Cabibbo-Kobayashi-Maskawa夸克混合矩阵的基本量之一。用柯古特-苏斯金德夸克作用对这个量的猝灭计算正在进行中。到目前为止，已经收集了6个晶格间距的数据，并计划再计算一个晶格间距。总而言之，这些数据应该允许将B参数精确地外推到连续统极限。基于今年发展的手征Ward恒等式方法的威尔逊夸克作用的类似计算也在进行中。(2)对于CP破坏研究来说，另一个重要的参数是B介子衰变常数。1995年初夏进行的初步计算显示，统计上的波动很大。对减小误差的抹源方法进行了试验，并于1995年底重新进行了计算。已经收集了两个晶格间距的数据，并计划很快开始进一步减少晶格间距的计算。这将使我们能够估计衰变常数的连续m值。(3)克洛弗夸克作用的测试已经完成，预计将更快地接近连续统极限。真正的计算将在(2)中的威尔逊计算完成后立即开始，我们预计能够在1996年夏天公布这些计算的最终结果。较少

项目成果

S.Aoki: "Manifestation of sea quark effects in the strong csupling constant" Physical Reuew Letters. 74. 22-25 (1995)

S.Aoki：“强夸克常数中海夸克效应的表现”《物理评论快报》。

M.Fukugita, Y.Kuramashi, M.Okawa and A.Ukawa: "Proton spin structure in lattice QCD" Physical Review Letters. 75. 2092 (1995)

M.Fukugita、Y.Kuramashi、M.Okawa 和 A.Ukawa：“晶格 QCD 中的质子自旋结构”物理评论快报。

S.Aoki, A.Ukawa and T.Umemura: "Phase structure of lattice QCD with Wilson quark action" Physical Review Letters. 76. 873 (1996)

S.Aoki、A.Ukawa 和 T.Umemura：“具有威尔逊夸克作用的晶格 QCD 的相结构”物理评论快报。

A.Ukawa: "Status of the CP-PACS project" Nuclear Physics (Proc.Suppl.). 42. 194 (1995)

A.Ukawa：“CP-PACS 项目的现状”核物理（Proc.Suppl.）。

Y.Kuramashi: "N'meson mass in lattice QCD" Physical Review Letters. 72. 3448-3451 (1994)

Y.Kuramashi：“晶格 QCD 中的 N介子质量”物理评论快报。