论文标题
低$ p _ {\ rm t} $ hadro生产：从过去的数据到未来的机会
Quarkonium polarization in low-$p_{\rm T}$ hadro-production: from past data to future opportunities
论文作者
论文摘要
Several fixed-target experiments reported J/$ψ$ and $Υ$ polarization measurements, as functions of Feynman $x$ ($x_{\rm F}$) and transverse momentum ($p_{\rm T}$), in three different polarization frames, using different combinations of beam particles, target nuclei and collision energies.数据形成了如此多样化和异质的图片，一见一见钟情，无法观察到明确的趋势。然而，更详细的外观使我们能够辨别出激发和支持简单解释的定性物理模式：直接产生的夸克尼亚是由gluon-gluon融合或夸克 - 易药的ni灭造成的，而以前的中源是完全纵向极化的，后者是完全极化的。该假设提供了在$ x _ {\ rm f} \ Lessim 0.5 $ Kinematical域中测得的J/$ψ$和$υ$（1S）极化的合理定量描述。我们提供可以使用质子和/或乳头束进行实验测试的预测，并表明改善了pion-nucleus碰撞中的J/$ψ$和$ψ$（2s）极化测量值可以对PION的鲜为人知的Parton分布功能提供重大约束。
Several fixed-target experiments reported J/$ψ$ and $Υ$ polarization measurements, as functions of Feynman $x$ ($x_{\rm F}$) and transverse momentum ($p_{\rm T}$), in three different polarization frames, using different combinations of beam particles, target nuclei and collision energies. The data form such a diverse and heterogeneous picture that, at first sight, no clear trends can be observed. A more detailed look, however, allows us to discern qualitative physical patterns that inspire and support a simple interpretation: the directly-produced quarkonia result from either gluon-gluon fusion or from quark-antiquark annihilation, with the former mesons being fully longitudinally polarized and the latter being fully transversely polarized. This hypothesis provides a reasonable quantitative description of the J/$ψ$ and $Υ$(1S) polarizations measured in the $x_{\rm F} \lesssim 0.5$ kinematical domain. We provide predictions that can be experimentally tested, using proton and/or pion beams, and show that improved J/$ψ$ and $ψ$(2S) polarization measurements in pion-nucleus collisions can provide significant constraints on the poorly known parton distribution functions of the pion.
