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arXiv 1902.04712hep-phhep-exhep-latnucl-th
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自旋为1的氘核Drell-Yan过程极化不对称性的理论预测和张量极化结构函数$b_1$

Theoretical predictions on polarization asymmetry for Drell-Yan process with spin-one deuteron and tensor-polarized structure function $b_1$

S. Kumano, Qin-Tao Song

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6 pages, 4 figures; Proceedings of 23rd International Spin Physics Symposium (SPIN2018), 10-14 September, 2018; Ferrara, Italy
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摘要：

本文报道了质子-氘核Drell-Yan过程中极化不对称性的最新理论研究进展，其中质子-氘核Drell-Yan过程是以极化的氘核为靶，结构函数为张量极化结构函数$b_1$ .在JLab对$b_1$和在Fermilab对Drell-Yan过程的实验测量是可能的。首先，我们给出了费米实验E1039中质子-氘核Drell-Yan不对称性的理论估计。我们进化张量极化部分子分布函数，解释现有的HERMES $b_1$数据，在$Q^2=2.5$ GeV $^2$的$Q^2$范围内的费米实验室Drell-Yan测量。然后，我们预测不对称性是百分之几的数量级。Drell-Yan实验在探测张量极化的反夸克分布方面具有优势，HERMES实验提出这是$b_1$（$\int dx b_1 (x) \ne 0$）的有限和.其次，我们预测$b_1$的JLab实验的标准卷积模型的氘核。我们的理论$b_1$结构函数似乎与HERMES数据有很大不同。此外，在质子的运动学极限$x_{max}=1$之外的非常大的$x$（$>1$）处存在显著的分布。由于标准的氘核模型估计与HERMES数据有很大的不同，如果未来的JLab数据与我们的传统预测有很大的不同，那么作为一个新的强子物理学领域，可能会有一个有趣的发展。

英文摘要：

We report recent theoretical progress on a polarization asymmetry in the proton-deuteron Drell-Yan process with a polarized-deuteron target and the tensor-polarized structure function $b_1$. Experimental measurements are possible at JLab for $b_1$ and at Fermilab for the Drell-Yan process. First, we show a theoretical estimate for the proton-deuteron Drell-Yan asymmetry in the Fermilab-E1039 experiment. We evolved tensor-polarized parton distribution functions, which explain existing HERMES $b_1$ data, at $Q^2=2.5$ GeV$^2$ to the $Q^2$ range of the Fermilab Drell-Yan measurements. Then, we predicted that the asymmetry is of the order of a few percent. The Drell-Yan experiment has an advantage to probe the tensor-polarized antiquark distributions, which were suggested by the HERMES experiment as a finite sum for $b_1$ ($\int dx b_1 (x) \ne 0$). Second, we predicted $b_1$ for the JLab experiment by the standard convolution model of the deuteron. Our theoretical $b_1$ structure function seems to be much different from the HERMES data. Furthermore, a significant distribution exists at very large $x$ ($>1$) beyond the kinematical limit $x_{max}=1$ for the proton. Because the standard deuteron-model estimate is much different from the HERMES data, there could be an interesting development as a new hadron-physics field if future JLab data will be much different from our conventional prediction.

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