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arXiv 0810.0045hep-lat
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动态(2+1)味畴壁费米子格点量子色动力学的核子结构

Nucleon structure with dynamical (2+1)-flavor domain wall fermions lattice QCD

Shigemi Ohta, Takeshi Yamazaki

摘要:

本文报道了RIKEN-BNL-Columbia(RBC)和UKQCD联合动力学(2+1)味畴壁费米子(VW)系综中核子的等矢量形状因子和等矢量结构函数的低阶矩。晶格截止估计为(a^{-1}=1.7)GeV。晶格体积大到2.7 fm。我们仔细优化核子源/汇分离的时间约为1.4 fm。在轴向电荷中发现了意想不到的大的有限尺寸效应,该效应与一个单变量,即π介子质量(m_π)与晶格空间线性范围(L)的乘积(m_πL)成比例,并在(m_πL = 5)附近开始。我们还讨论了矢量、诱导张量、轴矢量和诱导伪标量形状因子对动量转移的依赖性。从结构函数出发,给出了完全非微扰重整化的等矢量夸克动量分数(< x >_{u-d})、螺旋度分数(< x >_{Δu - Δd})和横动量(< 1 >_{δu - δd}),以及非重整化的扭曲系数(d_1)。动量与螺旋度比值(< x >_{u-d}/< x >_{Δu - Δd})与轻夸克质量无关,与实验符合得很好。它们各自的绝对值,完全重整化,显示出有趣的趋势,在最轻的轻夸克质量的各自的实验值。

英文摘要:

We report isovector form factors and low moments of isovector structure functions of nucleon from the coarse RIKEN-BNL-Columbia (RBC) and UKQCD joint dynamical (2+1)-flavor domain-wall fermions (DWF) ensembles. The lattice cut off is estimated at (a^{-1}=1.7) GeV. The lattice volume is as large as 2.7 fm across. We carefully optimize the nucleon source/sink separation in time to about 1.4 fm. Unexpectedly large finite-size effect in the axial charge is found. The effect scales with a single variable, the product (m_πL) of the pion mass (m_π) and lattice spatial linear extent (L), and sets in at around (m_πL = 5). We also discuss momentum-transfer dependence of the vector, induced tensor, axial-vector and induced pesudo-scalar form factors. From structure functions, fully non-perturbatively renormalized iso-vector quark momentum fraction, (< x >_{u-d}), helicity fraction, (< x >_{Δu - Δd}), and transversity, (< 1 >_{δu - δd}), are reported, as well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum to helicity fractions, (< x >_{u-d}/< x >_{Δu - Δd}), does not depend on light quark mass and agree well with the experiment. Their respective absolute values, fully renormalized, shows interesting trending toward the respective experimental values at the lightest light quark mass.

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