标题： 格点QCD计算的核子和负宇称核共振的光锥分布振幅 显示英文标题

标题： Light-cone Distribution Amplitudes of the Nucleon and Negative Parity Nucleon Resonances from Lattice QCD

摘要： 我们展示了基于两种味动态（clover）费米子的光锥分布振幅（DAs）的晶格研究结果，研究对象包括质子及其负宇称共振态，所用晶格具有不同的体积和从π介子质量为150 MeV起始的较小的pion质量。 我们发现质子中的三个价夸克以37% : 31% : 31%的比例分配动量，其中较大的份额对应携带质子螺旋性的u夸克，并且确定了位置空间中波函数在原点处的值，该值相对于基于QCD求和规则的现有估计来说较小。 高阶矩受到我们的数据约束，并且都在我们的不确定范围内与零一致。 我们还计算了与夸克角动量分布相关的高阶扭转DAs的归一化常数。 此外，我们使用变分法和定制的宇称投影算符来研究负宇称态。 通过这种方式，我们能够分离出两个最低态的贡献，我们认为它们可能分别对应N*(1535)和N*(1650)与π-核子连续态的混合态。 结果表明，我们识别为N*(1535)的态具有与第二观测到的负宇称态和质子都不同的DA，这可能解释了实验中观察到的N*(1535)和N*(1650)衰变模式的差异。 显示英文摘要

摘要： We present the results of a lattice study of light-cone distribution amplitudes (DAs) of the nucleon and negative parity nucleon resonances using two flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to m_pi = 150 MeV. We find that the three valence quarks in the proton share their momentum in the proportion 37% : 31% : 31%, where the larger fraction corresponds to the u-quark that carries proton helicity, and determine the value of the wave function at the origin in position space, which turns out to be small compared to the existing estimates based on QCD sum rules. Higher-order moments are constrained by our data and are all compatible with zero within our uncertainties. We also calculate the normalization constants of the higher-twist DAs that are related to the distribution of quark angular momentum. Furthermore, we use the variational method and customized parity projection operators to study the states with negative parity. In this way we are able to separate the contributions of the two lowest states that, as we argue, possibly correspond to N*(1535) and a mixture of N*(1650) and the pion-nucleon continuum, respectively. It turns out that the state that we identify with N*(1535) has a very different DA as compared to both the second observed negative parity state and the nucleon, which may explain the difference in the decay patterns of N*(1535) and N*(1650) observed in experiment.