$π^0$电解生产截面的Rosenbluth分离
Rosenbluth separation of the $π^0$ electroproduction cross section
摘要：
我们提出了深入的虚拟$π^0$电产生截面测量在$x_B$ =0.36和三个不同的$Q^2$ -值范围从1.5到2 GeV的$^2$，从实验E07-007在杰斐逊实验室的大厅A运行。Rosenbluth技术用于分离纵向和横向响应。结果表明，该体系的截面主要由横向分量决定，与微扰量子色动力学所预言的渐近极限相差甚远。非零纵向贡献的指示由也测量的干扰项$σ_{LT}$提供。结果进行了比较，几个模型的基础上的领导扭曲的方法广义Parton分布（GPD）。特别是，一个公平的协议获得的模型，其中的散射振幅描述的卷积的手征奇（transversity）的GPD的核子与扭曲-3 π分布振幅。因此，电产生中性π介子为通过实验获得横向GPD提供了令人兴奋的可能性。
英文摘要：
We present deeply virtual $π^0$ electroproduction cross-section measurements at $x_B$=0.36 and three different $Q^2$--values ranging from 1.5 to 2 GeV$^2$, obtained from experiment E07-007 that ran in the Hall A at Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component, and thus is far from the asymptotic limit predicted by perturbative Quantum Chromodynamics. An indication of a non-zero longitudinal contribution is provided by the interference term $σ_{LT}$ also measured. Results are compared with several models based on the leading twist approach of Generalized Parton Distributions (GPDs). In particular, a fair agreement is obtained with models where the scattering amplitude is described by a convolution of chiral-odd (transversity) GPDs of the nucleon with the twist-3 pion distribution amplitude. Therefore, neutral pion electroproduction may offer the exciting possibility of accessing transversity GPDs through experiment.
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