Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2012 Feb 3;108(5):052001. doi: 10.1103/PhysRevLett.108.052001. Epub 2012 Jan 30.
We report the first measurement of the double-spin asymmetry A{LT} for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized {3}He target. The kinematics focused on the valence quark region, 0.16<x<0.35 with 1.4<Q{2}<2.7 GeV{2}. The corresponding neutron A{LT} asymmetries were extracted from the measured {3}He asymmetries and proton over {3}He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g{1T}{q} and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π{-} production on {3}He and the neutron, while our π{+} asymmetries are consistent with zero.
我们报告了在横极化氚靶上进行的半单举深度非弹性电子散射中带电π介子的双自旋不对称 A{LT}的首次测量。该动力学研究集中在价夸克区域,0.16<x<0.35,1.4<Q{2}<2.7 GeV{2}。使用有效极化近似,从测量的氚不对称性和质子与氚的截面比中提取了对应的中子 A{LT}不对称性。这些新数据探测了横向动量相关的部分子分布函数 g{1T}{q},因此可以获得夸克自旋轨道关联。我们的结果表明,对于 3He 和中子上的π{-}产生存在正的方位不对称性,而我们的 π{+}不对称性则与零一致。