Weinberg角反常现象的理论解释

标准模型在过去20年中经历了大量的实验检验，已被人们所接受。Weinberg角（或称弱角）是标准模型中一个极其重要的物理量，它的精确值对于检验标准模型有着至关重要的作用。2002年，NuTeV实验组报道了他们测量到的Weinberg角的值与在其它电弱过程中测量到的该角的值不同。这一反常现象引起了人们极大的关注，无论能否在标淮模型的解释这种现象，对粒子物理都将是一个推进。为了解释这种反常现象，本文在标准模型的框架下，推导了核子海中奇异-反奇异夸克分布不对称对Paschos-Wolfenstein关系的修正，并计算了光推介子-重子波动模型和手征夸克模型下，奇异-反奇异夸克分布的不对称性，考查了这种不对称性对Weinberg角测量值的影响。结果表明，核子海中奇异-反奇异夸克分布的不对称性所引起的修正，能够在很大程度上降低NuTeV测量到的Weinberg角的值与标准模型预言值之间的差异，可以作为NuTeV反常现象的一种合理的解释。

THEORETICAL EXPLANATIONS FOR THE WEINBERG ANGLE ANOMALY

Weinberg angle (or weak angle) is so important that it can partly confirm the Standard Model (SM), which has been widely accepted because the predictions in the SM are consistent with the experiment data in the last twenty years. In 2002, the value of Weinberg angle reported by the NuTeV collaboration is different from the world average value measured in other electroweak processes. An extensive attention has been paid to this anomaly, because it would shed light on particle physics whether it can be explained or not within the Standard Model. In order to explain this discrepancy, we obtained the correction to the Paschos-Wolfenstein relation when the distributions of strange quark-antiquark are asymmetric within the SM. In this work, we calculated the asymmetry of strange quark-antiquark distributions in the nucleon by using the light-cone meson-baryon fluctuation model and the chiral quark model and gained similar results. As a result, we found that the correction due to the asymmetry of the strange quark-antiquark distributions can remove the NuTeV anomaly to a great extent, which implies that asymmetric strange-antistrange quark distributions may be a reasonable explanation for the NuTeV defect.