标题： 介电子电产的方位自旋不对称性 显示英文标题

标题： Azimuthal Spin Asymmetries of Pion Electroproduction

摘要： 方位角自旋不对称性，包括在非极化带电轻子束与纵向和横向极化核子靶的半独占深度非弹性散射中产生的带电和中性π介子，被分析和计算。 在这些计算中常使用的夸克分布和碎裂函数的各种假设和近似被详细研究。 发现不同的分布和碎裂函数方法可能导致在HERMES实验中测量的方位角不对称性有相当不同的预测，因此在将现有数据用作夸克横向分布测量之前应考虑这些影响。 还发现，对于从质子靶产生的$\pi^-$，必须考虑非偏好夸克到π介子的碎裂函数，尽管它们可以忽略对于$\pi^+$和$\pi^0$的产生。 从质子靶产生的π介子适合研究$u$夸克横向分布，而质子和中子靶产生的π介子的组合可以测量夸克横向分布的味结构。 显示英文摘要

摘要： Azimuthal spin asymmetries, both for charged and neutral pion production in semi-inclusive deep inelastic scattering of unpolarized charged lepton beams on longitudinally and transversely polarized nucleon targets, are analyzed and calculated. Various assumptions and approximations in the quark distributions and fragmentation functions often used in these calculations are studied in detail. It is found that different approaches to the distribution and fragmentation functions may lead to quite different predictions on the azimuthal asymmetries measured in the HERMES experiments, thus their effects should be taken into account before using the available data as a measurement of quark transversity distributions. It is also found that the unfavored quark to pion fragmentation functions must be taken into account for $\pi^-$ production from a proton target, although they can be neglected for $\pi^+$ and $\pi^0$ production. Pion production from a proton target is suitable to study the $u$ quark transversity distribution, whereas a combination of pion production from both proton and neutron targets can measure the flavor structure of quark transversity distributions.