论文标题
$ \ cos 2 ϕ $ Azimuthal不对称性的TMD进化研究在EIC $ j/ψ$生产
TMD Evolution Study of the $\cos 2 ϕ$ Azimuthal Asymmetry in Unpolarized $J/ψ$ Production at EIC
论文作者
论文摘要
Electron-Proton碰撞中的半包含$ J/ψ$是研究未来电子离子撞机的GLUON横向动量分布（TMD）的有前途的过程。在本文中，我们改进了对$ \ cos 2 ϕ $方位角不对称的先前研究，该研究来自非偏振质子内部通过包括TMD演化的线性极化。我们发现，在TMD制度中，不对称性会随着$ J/ψ$的横向动量的增加而单调增长，与使用高斯TMD的树级计算相反。我们对EIC不对称的预测可能会在较大的$ x $，$ Q $和横向动量时变得非常大，甚至比积极界限还大。这个问题源于非常小的$ b $区域，这意味着TMD分解的一系列有效性范围比通常预期的更受限制。我们还包括对大型$ b $区域的非扰动不确定性的估计，我们得出的结论是，它小于最大的不确定性来源，这源于颜色八位八距离长距离矩阵元素的选择。
Semi-inclusive $J/ψ$ production in electron-proton collisions is a promising process to study gluon transverse momentum distributions (TMDs) at the future Electron-Ion Collider. In this article, we improve on previous studies of the $\cos 2 ϕ$ azimuthal asymmetry that arises from the linear polarization of gluons inside unpolarized protons by including TMD evolution. We find that in the TMD regime the asymmetry grows monotonically with increasing transverse momentum of the outgoing $J/ψ$, in contrast to tree level calculations with Gaussian TMDs. Our predictions for the asymmetry at EIC can become very large at larger $x$, $Q$, and transverse momenta, even larger than the positivity bound. This problem stems from the very small $b$ region and implies a range of validity of TMD factorization that is more restricted than usually expected. We also include an estimate of the nonperturbative uncertainty from the large $b$ region and we conclude that it is smaller than the largest source of uncertainty, which stems from the choice of Color Octet Long-Distance Matrix Elements.
